#8 #9 #11wa了

#include <bits/stdc++.h>

#define N 500010
#define MAXX 1000000000001

using namespace std;
int n, m, s, t;
int u,v;
long long w;
long long ans, dis[N];
int tot = 1;
int now[N], head[N];

struct node {
	int to, nxt;
	long long val;
}e[N];

inline void add(int u, int v, long long w) {
	e[++tot].to = v;
	e[tot].val += w;
	e[tot].nxt = head[u];
	head[u] = tot;
	
	e[++tot].to = u;
	e[tot].val += 0;
	e[tot].nxt = head[v];
	head[v] = tot;
}

inline int bfs() {
    for(int i = 1; i <= n; ++i) {
        dis[i] = MAXX;
    }
	queue<int> q;
	q.push(s);
	dis[s] = 0;
	now[s] = head[s];
	while(!q.empty()) {
		int x = q.front();
		q.pop();
		for(int i = head[x]; i; i = e[i].nxt) {
			int v = e[i].to;
			if(e[i].val > 0 && dis[v] == MAXX) {
				q.push(v);
				now[v] = head[v];
				dis[v] = dis[x] + 1;
				if(v == t) 
                    return 1;
			}
		}
	}
	return 0;
}

inline int dfs(int x, long long sum) { 
	if(x == t) 
        return sum;
	long long k, res = 0;
	for(int i = now[x]; i && sum; i = e[i].nxt) {
		now[x] = i; 
		int v = e[i].to;
		if(e[i].val > 0 && (dis[v] == dis[x] + 1)) {
			k = dfs(v, min(sum, e[i].val));
			if(k == 0) 
                dis[v] = MAXX; 
			e[i].val -= k;
			e[i ^ 1].val += k;
			res += k; 
			sum -= k; 
		}
	}
	return res;
}

int main() {
	cin >> n >> m >> s >> t;
	for(int i = 1; i <= m; ++i) {
		cin >> u >> v >> w;
		add(u, v, w);
	}
	while(bfs())
		ans += dfs(s, MAXX);
	cout << ans << endl;
	return 0;
}