#include <cstdio>
#include <queue>
#include <vector>
using namespace std;
queue <int> Q;
vector <pair <int,int> > G[30005];
int n,m,x,y,i,xx,yy,dist[30005],crt,distance,d,s;
int main()
{
    freopen("sate.in","r",stdin);
    freopen("sate.out","w",stdout);
    scanf("%d %d %d %d",&n,&m,&x,&y);
    for (i=1; i<=m; i++)
    {
        scanf("%d %d %d",&xx,&yy,&d);
        G[xx].push_back(make_pair(yy,d));
        G[yy].push_back(make_pair(xx,d));
        s=x;
    }
    for (i=1; i<=n; i++) dist[i]=-1;
    dist[s]=0;
    Q.push(s);
    while (!Q.empty())
    {
        crt=Q.front();
        Q.pop();
        for (i=0; i<G[crt].size(); i++)
        {
            if (dist[G[crt][i].first]==-1)
            {
                Q.push(G[crt][i].first);
                if (G[crt][i].first<s && s<=crt) dist[G[crt][i].first]=G[crt][i].second-dist[crt];
                if (G[crt][i].first<crt && crt<=s) dist[G[crt][i].first]=G[crt][i].second+dist[crt];
                if (s<G[crt][i].first && G[crt][i].first<crt) dist[G[crt][i].first]=dist[crt]-G[crt][i].second;
                if (crt<G[crt][i].first && G[crt][i].first<s) dist[G[crt][i].first]=dist[crt]-G[crt][i].second;
                if (s<=crt && crt<G[crt][i].first) dist[G[crt][i].first]=G[crt][i].second+dist[crt];
                if (crt<=s && s<G[crt][i].first) dist[G[crt][i].first]=G[crt][i].second-dist[crt];
            }
        }
    }
    if (s<=x && s<=y) {printf("%d\n",dist[y]-dist[x]); return 0;}
    if (s<=y && y<=x) {printf("%d\n",dist[x]-dist[y]); return 0;}
    if (x<=s && s<=y) {printf("%d\n",dist[x]+dist[y]); return 0;}
    if (y<=s && s<=x) {printf("%d\n",dist[x]+dist[y]); return 0;}
    if (x<=y && y<=s) {printf("%d\n",dist[x]-dist[y]); return 0;}
    if (y<=x && x<=s) {printf("%d\n",dist[y]-dist[x]); return 0;}
    return 0;
}