#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
#define int long long
using namespace std;
const int N = 205,M = 5005;
int n,m,s,t,tot = 1;
int flows[N],head[N],lv[N],cur[N];
struct node{
    int to,next,w;
}eg[M*2];
void adde(int a,int b,int w){
    eg[++tot] = {b,head[a],w},head[a] = tot;;
}
void add(int a, int b, int c)
{
    adde(a,b,c);
    adde(b,a,0);
}
bool bfs(){
	memset(lv,-1,sizeof lv);
	memcpy(cur,head,sizeof head);
	queue<int> q;
	lv[s] = 0;
	q.push(s);
	while(q.size()){
		int u = q.front();q.pop();
		for(int i = head[u];i;i = eg[i].next){
			int val = eg[i].w,y = eg[i].to;
			if(val > 0 && lv[y] == -1){
				lv[y] = lv[u] + 1;
				q.push(y);
			}
		}
	}
	return lv[t] != -1;
}
int dfs(int flow,int u){
	if(u == t) return flow;
	int lass = flow;
	for(int i = cur[u];i && lass;i = eg[i].next){
	    cur[u] = i;
		int y = eg[i].to,val = eg[i].w;
		if(val > 0 && lv[y] == lv[u]+1){
    		int c = dfs(min(val,flow),y);
    		lass -= c;
    		eg[i].w -= c;
    		eg[i^1].w += c;
		}
	}
	return flow - lass;
}
int Dinic(){
	int ans = 0;
	while(bfs())
		ans += dfs(inf,s);
	return ans;
}
signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
	cin >> n >> m >> s >> t;
	int u,v,w;
	for(int i = 1;i <= m;i ++){
	    cin >> u >> v >> w;
	    add(u,v,w);
	}
	cout << Dinic();
	return 0;
}

提交记录，#5,6,10 WA