萌新求救！！！

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
int n,m,s,t;
int d[100005];
int e[1000005],v[1000005],lst[100005],nxt[1000005],cnt;
int read()
{
    int ans=0;
    char c=getchar();
    for(;c<'0'||c>'9';c=getchar());
    for(;'0'<=c&&c<='9';c=getchar())
        ans=ans*10+c-'0';
    return ans;
}
void Build(int x,int y,int z)
{
    e[++cnt]=y;
    nxt[cnt]=lst[x];
    lst[x]=cnt;
    v[cnt]=z;
    e[++cnt]=x;
    nxt[cnt]=lst[y];
    lst[y]=cnt;
    v[cnt]=0;
}
int ans=0;
bool bfs(int s,int t)
{
    queue<int> q;
    memset(d,0,sizeof(d));
    q.push(s);
    d[s]=1;
    while(!q.empty())
    {
        int x=q.front();
        for(int u=lst[x];u;u=nxt[u])
            if(!d[e[u]]&&v[u])
            {
                d[e[u]]=d[x]+1;
                if(e[u]==t) return true;
                q.push(e[u]);
            }
        q.pop();
    }
    return false;
}
int dfs(int x,int c)
{
    if(c==0||x==t) return c;
    int ans=0;
    for(int u=lst[x];u;u=nxt[u])
    {
        int y=e[u];
        if(d[x]+1==d[y]&&v[u])
        {
            int p=dfs(y,min(c-ans,v[u]));
            v[u]-=p;
            v[u^1]+=p;
            ans+=p;
        }
        if(ans==c) break;
    }
    return ans;
}
int main()
{
    n=read(),m=read(),s=read(),t=read();
    for(int i=1;i<=m;i++)
    {
        int x=read(),y=read(),z=read();
        Build(x,y,z);
    }
    while(bfs(s,t)) ans+=dfs(s,(1<<30)-1+(1<<30));
    printf("%d\n",ans);
    return 0;
}