用堆优化版的dij，算出来最短路再处理询问。

CODE：

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
#define x first
#define y second
#define sz(a) a.size()
#define lowbit(x) (x & -x)
#define debug(x) cout << #x << ':' << x << endl
#define VI vector<int> 
#define all(a) a.begin(), a.end()
#define rep(i, c, n) for (int i = c; i <= n; ++i)
#define per(i, c, n) for (int i = c; i >= n; --i)
#define w(x) while(x --)
#define db double
#define pb(x) push_back(x)
const int INF = 0x3f3f3f3f;
const ll INFll = 9223372036854775807;
const double PI = 3.1415926;
#define getchar() (tt == ss && (tt = (ss = In) + fread(In, 1, 1 << 20, stdin), ss == tt) ? EOF : *ss++)
char In[1 << 20], *ss=In, *tt=In;
namespace Fastio
{
	struct Reader
	{
		template <typename T> Reader& operator >> (T &x)
		{
			x = 0;
			short f = 1;
			char c = getchar();
			while (c < '0' || c > '9') { if (c == '-') f *= -1; c = getchar(); }
			while (c >= '0' && c <= '9') x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
			x *= f;
			return *this;
		}
		Reader& operator >> (double &x)
		{
			x = 0;
			double t = 0;
			short f = 1, s = 0;
			char c = getchar();
			while ((c < '0' || c > '9') && c != '.') { if (c == '-') f *= -1; c = getchar(); }
			while (c >= '0' && c <= '9' && c != '.') x = x * 10 + (c ^ 48), c = getchar();
			if (c == '.') c = getchar();
			else { x *= f; return *this; }
			while (c >= '0' && c <= '9') t = t * 10 + (c ^ 48), s++, c = getchar();
			while (s--) t /= 10.0;
			x = (x + t) * f;
			return *this;
		}
		Reader& operator >> (long double &x)
		{
			x = 0;
			long double t = 0;
			short f = 1, s = 0;
			char c = getchar();
			while ((c < '0' || c > '9') && c != '.') { if (c == '-') f *= -1; c = getchar(); }
			while (c >= '0' && c <= '9' && c != '.') x = x * 10 + (c ^ 48), c = getchar();
			if (c == '.') c = getchar();
			else { x *= f; return *this; }
			while (c >= '0' && c <= '9') t = t * 10 + (c ^ 48), s++, c = getchar();
			while (s--) t /= 10.0;
			x = (x + t) * f;
			return *this;
		}
		Reader& operator >> (__float128 &x)
		{
			x = 0;
			__float128 t = 0;
			short f = 1, s = 0;
			char c = getchar();
			while ((c < '0' || c > '9') && c != '.') { if (c == '-') f *= -1; c = getchar(); }
			while (c >= '0' && c <= '9' && c != '.') x = x * 10 + (c ^ 48), c = getchar();
			if (c == '.') c = getchar();
			else { x *= f; return *this; }
			while (c >= '0' && c <= '9') t = t * 10 + (c ^ 48), s++, c = getchar();
			while (s--) t /= 10.0;
			x = (x + t) * f;
			return *this;
		}
		Reader& operator >> (char &c)
		{
			c = getchar();
			while (c == ' ' || c == '\n' || c == '\r') c = getchar();
			return *this;
		}
		Reader& operator >> (char *str)
		{
			int len = 0;
			char c = getchar();
			while (c == ' ' || c == '\n' || c == '\r') c = getchar();
			while (c != ' ' && c != '\n' && c != '\r') str[len++] = c, c = getchar();
			str[len] = '\0';
			return *this;
		}
		Reader& operator >> (string &str)
		{
			str.clear();
			char c = getchar();
			while (c == ' ' || c == '\n' || c == '\r') c = getchar();
			while (c != ' ' && c != '\n' && c != '\r') str.push_back(c), c = getchar();
			return *this;
		}
		Reader() {}
	} cin;
	const char endl = '\n';
	struct Writer
	{
		const int Setprecision = 6;
		typedef int mxdouble;
		template <typename T> Writer& operator << (T x)
		{
			if (x == 0) { putchar('0'); return *this; }
			if (x < 0) putchar('-'), x = -x;
			static short sta[40];
			short top = 0;
			while (x > 0) sta[++top] = x % 10, x /= 10;
			while (top > 0) putchar(sta[top] + '0'), top--;
			return *this;
		}
		Writer& operator << (double x)
		{
			if (x < 0) putchar('-'), x = -x;
			mxdouble _ = x;
			x -= (double)_;
			static short sta[40];
			short top = 0;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			if (top == 0) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			putchar('.');
			for (int i = 0; i < Setprecision; i++) x *= 10;
			_ = x;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			for (int i = 0; i < Setprecision - top; i++) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			return *this;
		}
		Writer& operator << (long double x)
		{
			if (x < 0) putchar('-'), x = -x;
			mxdouble _ = x;
			x -= (long double)_;
			static short sta[40];
			short top = 0;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			if (top == 0) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			putchar('.');
			for (int i = 0; i < Setprecision; i++) x *= 10;
			_ = x;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			for (int i = 0; i < Setprecision - top; i++) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			return *this;
		}
		Writer& operator << (__float128 x)
		{
			if (x < 0) putchar('-'), x = -x;
			mxdouble _ = x;
			x -= (__float128)_;
			static short sta[40];
			short top = 0;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			if (top == 0) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			putchar('.');
			for (int i = 0; i < Setprecision; i++) x *= 10;
			_ = x;
			while (_ > 0) sta[++top] = _ % 10, _ /= 10;
			for (int i = 0; i < Setprecision - top; i++) putchar('0');
			while (top > 0) putchar(sta[top] + '0'), top--;
			return *this;
		}
		Writer& operator << (char c) { putchar(c); return *this; }
		Writer& operator << (char *str)
		{
			int cur = 0;
			while (str[cur]) putchar(str[cur++]);
			return *this;
		}
		Writer& operator << (const char *str)
		{
			int cur = 0;
			while (str[cur]) putchar(str[cur++]);
			return *this;
		}
		Writer& operator << (string str)
		{
			int st = 0, ed = str.size();
			while (st < ed) putchar(str[st++]);
			return *this;
		}
		Writer() {}
	} cout;
}
using namespace Fastio;
#define cin Fastio::cin
#define cout Fastio::cout
#define endl Fastio::endl
#define max(a,b) a > b ? a : b
#define min(a,b) a<b?a:b
#define abs(x) x<0?-x:x
template<typename T>inline T power(T a, T b) {T res = 1;while (b) {if (b & 1) res = res * a;a = a * a;b >>= 1;}return res;}
const int N = 50010;
int n, m, q;
int e[N], w[N], ne[N], h[N], idx;
int dist[N];
bool st[N];
void add(int a, int b, int c) {
	e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx ++;
}
void dijkstra() {
    memset(dist, 0x3f, sizeof(dist));
    dist[1] = 0;
    priority_queue<PII, vector<PII>, greater<PII>> heap;
    heap.push({0, 1});
    while (heap.size()) {
        auto t = heap.top();
        heap.pop();
        int v = t.second;
        if (st[v]) continue;
        st[v] = true;
        for (int i = h[v]; ~i; i = ne[i]) {
            int j = e[i];
            if (dist[j] > dist[v] + w[i]) {
                dist[j] = dist[v] + w[i];
                heap.push({dist[j], j});
            }
        }
    }
}
int main() {
	// freopen("P2984_2.in", "r", stdin);
	// freopen("Myoutput", "w", stdout);
	cin >> n >> m >> q;
	memset(h, -1, sizeof(h));
	while(m --) {
		int a, b, c;
		cin >> a >> b >> c;
		add(a, b, c);
		add(b, a, c);
	}
	dijkstra();
	while (q--) {
		int x, y;
		cin >> x >> y;
		cout << dist[x] + dist[y] << endl;
	}
	return 0;
}