#include<bits/stdc++.h>
#define inf (1<<30)
#define N 11010
#define M 120010
using namespace std;
int n,m,s,t,sum,cc[N],use[N],yflow[N],flag[N],cntcc[N];
struct cmp {
	bool operator()(int a,int b) const {
		return cc[a]<cc[b];
	}
};
priority_queue<int,vector<int>,cmp> q;
struct node {
	int to,next,val;
} e[M<<1];
int head[N],last[N];
void add(int x,int y,int val,int id) {
	if(head[x]==0) head[x]=id;
	else e[last[x]].next=id;
	last[x]=id,e[id].val=val,e[id].to=y;
} 
void bfs() {
	for(int i = 1; i <= n; i++) cc[i] = inf;
	use[1]=t,cc[t]=0;
	int u=0,v=1;
	while(u<v) {
		++u;
		int fst=use[u];
		for(int i = head[fst]; i != 0; i = e[i].next) {
			if(cc[e[i].to]!=inf) continue;
			if(e[i^1].val==0) continue;
			++v,cc[e[i].to]=cc[fst]+1,use[v]=e[i].to;
		}
	}
	use[s]=n;
}
void HLPP() {
	bfs();
	if(cc[s]==inf) return;
	cc[s]=n;
	for(int i = 1; i <= n; i++) if(cc[i] != inf) cntcc[cc[i]]++;
	for(int i = head[s]; i != 0; i = e[i].next) {
		yflow[e[i].to] = e[i].val , e[i^1].val += e[i].val , e[i].val = 0;
		if(e[i].to!=s&&e[i].to!=t&&flag[e[i].to]==0) flag[e[i].to]=1,q.push(e[i].to);
	}
	while(!q.empty()) {
		int now = q.top();
		q.pop();
		flag[now]=0;
		if(cc[now]==n+1) continue;
		for(int i = head[now]; i != 0; i = e[i].next) if(cc[now]==cc[e[i].to]+1) {
			int flow=min(yflow[now],e[i].val);
			if(flow == 0) continue;
			e[i].val-=flow,e[i^1].val+=flow;
			yflow[now]-=flow,yflow[e[i].to]+=flow;
			if(e[i].to!=s&&e[i].to!=t&&flag[e[i].to]==0) flag[e[i].to]=1,q.push(e[i].to);
		}
		if(yflow[now]) {
			--cntcc[cc[now]];
			if(cntcc[cc[now]]==0) for(int i = 1; i <= n; i++) if(cc[i]>cc[now]&&i!=s&&i!=t&&cc[now]<=now) cc[now]=n+1;
			cc[now]=n+1;
			for(int i = head[now]; i != 0; i = e[i].next) if(e[i].val) cc[now]=min(cc[e[i].to]+1,cc[now]);
			++cntcc[cc[now]];
			flag[now]=1,q.push(now);
		}		
	}
}
signed main() {
	int x,y,z;
	scanf("%d%d%d%d",&n,&m,&s,&t);
	for(int i = 1; i <= m; i++) {
		scanf("%d%d%d",&x,&y,&z);
		add(x,y,z,i*2);
		add(y,x,0,i*2+1);
	}
	HLPP();
	printf("%d\n",yflow[t]);
	return 0;
}

HLPP求助,禁止无意义评论