#include <fstream>
#include <vector>
using namespace std;


#define pb push_back
#define mp make_pair
#define to first
#define cost second

vector<pair<int, int> > G[30010];
int N, M, X, Y, A, B, C, used[30010];

void DFS(int start, int dist);

int main()
{
    ifstream in("sate.in");
    ofstream out("sate.out");
    int i;
    in >> N >> M >> X >> Y;
    for(i = 1; i <= M; i++)
    {
          in >> A >> B >> C;
          G[A].pb(mp(B, C));
          G[B].pb(mp(A, C));
    }
    DFS(X, 0);
    return 0;
}

void DFS(int start, int dist)
{
     if(start == Y) 
     {
              out << dist << " ";
              exit(0);
     }
     used[start] = 1;
     vector<pair<int, int> > :: iterator it;
     for(it = G[start].begin(); it != G[start].end(); ++ it)
     {
        if(!used[it -> to])
        {
            if(it -> to < start)
            {
                   dist -= it -> cost;
                   DFS(it -> to, dist);
                   dist += it -> cost;
            }else
            {
                 if(it -> to > start)
                 {
                       dist += it -> cost;
                       DFS(it -> to, dist);
                       dist -= it -> cost;
                 }
            }
        }
     }
}