#include <cstdio>
#include <vector>

using namespace std;

FILE *fin = fopen("sate.in", "r");
FILE *fout = fopen("sate.out", "w");

int n,m,i,x,y,x1,y1,cost,sol,s,ok,v[30005];
vector< pair<int, int> > L[30005];

void dfs(int nod)
{
    if (!ok)
    {
        v[nod] = 1;
        if (nod == y)
        {
            sol = s;
            ok = 1;
        }
        for (int i=0; i<L[nod].size(); ++i)
        {
            int vecin = L[nod][i].first; int cost = L[nod][i].second;
            if (!v[vecin])
            {
                if (vecin > nod)
                    s += cost;
                else
                    s -= cost;
                dfs(vecin);
                if (vecin > nod)
                    s -= cost;
                else
                    s += cost;
            }
        }
    }
}

int main()
{
    fscanf(fin, "%d%d%d%d", &n, &m, &x, &y);
    for (i=1; i<=m; ++i)
    {
        fscanf(fin, "%d%d%d", &x1, &y1, &cost);
        L[x1].push_back(make_pair(y1, cost));
        L[y1].push_back(make_pair(x1, cost));
    }
    dfs(x);
    fprintf(fout, "%d", sol);
    return 0;
}