#include <fstream>

using namespace std;
ifstream fin("sate.in");
ofstream fout("sate.out");
int n,m,x,y,a[3000][3000],v[3000],u,p,c[3000],s;
void dfs(int k)
{
    int i;
    u++;
    c[u]=k;
    v[k]=1;
    if(k==y){
        fout<<s;
        fout.close();
    }
    for(i=1;i<=n;i++)
        if(a[k][i]>0 && v[i]==0){
            if(k>i)
                s=s-a[k][i];
            else
                s=s+a[k][i];
            dfs(i);
            if(k>i)
                s=s+a[k][i];
            else
                s=s-a[k][i];
        }
}
int main()
{
    fin>>n>>m>>x>>y;
    int x1,x2,i,d;
    for(i=1;i<=m;i++)
    {
        fin>>x1>>x2>>d;
        a[x1][x2]=d;
        a[x2][x1]=d;
    }
    dfs(1);
    return 0;
}