#include <bits/stdc++.h>
using namespace std;

const int M = 5005, N = 201;
struct Edge {
	int next, to, val;
} edge[M * 2];
struct Pre {
	int next, val;
} pre[N];
int h[N], vis[N], n, m, s, t, cnt;
queue<int> q;
void add(int u, int v, int w) {
	edge[++cnt] = { h[u], v, w }, h[u] = cnt;
}
bool bfs(int s, int t) {
	while (!q.empty())
		q.pop();
	memset(vis, 0, sizeof(int) * (n + 1));
	memset(pre, 0, sizeof(Pre) * (n + 1));
	q.push(s);
	vis[s] = 1;
	int u, v, d;
	while (!q.empty()) {
		u = q.front(), q.pop();
		if (u == t)
			return true;
		for (int i = h[u]; i; i = edge[i].next) {
			v = edge[i].to, d = edge[i].val;
			if (d && !vis[v])
				pre[v] = { u, i }, q.push(v), vis[v] = 1;
		}
	}
	return false;
}
void read() {
	cin >> n >> m >> s >> t;
	int l, r, w;
	for (int i = 1; i <= m; i++) {
		scanf("%d %d %d", &l, &r, &w);
		add(l, r, w);// add(r, l, 0);
	}
}
int arg(int s, int t) {
	int minn = 0x3f3f3f3f;
// for (int i = t; i != s; i = pre[i].next)
//  printf("pre[%d]:{%d %d}", i, pre[i].next, edge[pre[i].val].val);
// puts("");
	for (int i = t; i != s; i = pre[i].next)
		minn = min(minn, edge[pre[i].val].val);
	for (int i = t; i != s; i = pre[i].next)
		edge[pre[i].val].val -= minn;// edge[pre[i].val ^ 1].val += minn;
// for (int i = t; i != s; i = pre[i].next)
//  printf("pre[%d]:{%d %d}", i, pre[i].next, edge[pre[i].val].val);
	return minn;
}
long long EK(int s, int t) {
	long long cnt = 0;
	while (bfs(s, t)) {
		cnt += arg(s, t);
//  printf("%lld\n", cnt);
	}
	return cnt;
}
int main() {
	read();
	cout << EK(s, t);
	return 0;
}

看读入 连反向边都没建 pre的val代表那条边的编号