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

ifstream f("sate.in");
ofstream g("sate.out");

int n,m,x2,y2,viz[30002],s=0;
vector< pair<int,int> >v[30002];
vector< pair<int,int> >w[30002];
queue< pair<int,int> >q;

void bfs(int x)
{
    viz[x]=1;
    q.push(make_pair(x,0));
    while(!q.empty())
    {
        int nod=q.front().first;
        q.pop();
        for(auto it:v[nod])
        {
            if(viz[it.first]==0)
            {
                int nou=it.first;
                int cost=it.second;
                s+=cost;
                viz[nou]=1;
                q.push(make_pair(nou,cost));
            }
        }
        for(auto it:w[nod])
        {
            if(viz[it.first]==0)
            {
                int nou1=it.first;
                int c1=it.second;
                s-=c1;
                viz[nou1]=1;
                q.push(make_pair(nou1,c1));
            }
        }
    }
}

int main()
{
    int i,x,y,c;
    f>>n>>m>>x2>>y2;
    for(i=1; i<=m; i++)
    {
        f>>x>>y>>c;
        v[x].push_back(make_pair(y,c));
        w[y].push_back(make_pair(x,c));
    }
    bfs(x2);
    g<<s;
    return 0;
}