#include <iostream>
#include <fstream>
#include <queue>
#include <stack>
#include <vector>

using namespace std;
int mat[20000][20000];
int n, viz[20000], numar, m, lant;


void bf(int start, int end )
{
    int  j, x, dist = 0;
    queue < int > c;

    c.push( start );
    viz[ start ] = 1;

    while ( !c.empty() )
    {
        x = c.front();
        c.pop();


        for ( j = 1; j <= n; j++ )

            if( mat[ x ][ j ] && !viz[ j ]  )
            {
                c.push( j );
                viz[ j ] = 1;
                if ( x < j )

                    dist += mat[ x ][ j ];
                else

                    dist -= mat[ x ] [ j ];

                if ( j == end )

                    goto loop1;

            }


    }
    return;
    loop1:
        ofstream g("sate.out");
        g << dist;
        //cout<< dist;
}

int main()
{
    ifstream f( "sate.in" );



    int i, j, k, lung, x, y;

    f >> n >> m;
    f >> x >> y;

    for ( i = 1; i <= m ; i++ )
    {
        f >> j >> k >> lung;
        mat[ j ] [ k ] = mat[ k ][ j ] = lung;
    }
    f.close();


    bf( x, y );




    return 0;
}