#include <iostream>

#include <fstream>

#include <vector>

using namespace std;

long long s=0,n,m,x,y,nr,maxi=-609,benis,a,b,b1,b2,visitat[100001];

struct pc
{

    int nod;

    long long dist;

} cd;

vector<pc>v[100001];

vector<int>bn;

void filix(int x,int dest,int nmr)

{

    visitat[x]=1;

    if(x==dest)

        s=nmr;

    for(int i=0; i<v[x].size(); i++)

    {

        if(visitat[v[x][i].nod]==0)

        {

            nmr+=v[x][i].dist;

            filix(v[x][i].nod,dest,nmr);

            nmr-=v[x][i].dist;

        }

    }

}



int main()

{

    ifstream in("sate.in");

    ofstream out("sate.out");

    in>>n>>m>>x>>y;

    for(int i=1; i<=m; i++)

    {

        in>>a>>b>>nr;

        cd.nod=a;

        cd.dist=-nr;

        v[b].push_back(cd);

        cd.nod=b;

        cd.dist=nr;

        v[a].push_back(cd);

    }

    filix(x,y,0);

    out<<s<<' ';



    return 0;

}

//adiacenta