#include<bits/stdc++.h>
using namespace std;
const int N = 105;
const int INF = 100000000;
int n,m,a,b,d[N],e[N][N],w[N][N],ans,vst[N],ok[N];
vector<int> tmp[N];
void dijkstra(){
    for(int i=0;i<=n;i++) d[i]=INF; d[a]=0;
    for(int c=1;c<=n;c++){
        int v=0; for(int i=1;i<=n;i++) if(!ok[i]&&d[i]<d[v]) v=i;
        ok[v]=1;
        for(int u = 1; u <= n; u++){
            if(!e[v][u]) continue;
            if(d[u]>d[v] + w[v][u]) d[u] = d[v] + w[v][u], tmp[u].clear(), tmp[u].push_back(v);
            else if(d[u] == d[v] + w[v][u]) tmp[u].push_back(v);
        }
    }
}
void bfs(){
    queue<int> q; q.push(b);
    while(!q.empty()){
        int nw = q.front(); q.pop();
        for(int i=0;i<tmp[nw].size();i++){
            int l = tmp[nw][i];
            ans -= w[l][nw];
            if(vst[l]) continue;
            q.push(l); vst[l]=1;
        }
    }
}
int main(){
    cin>>n>>m>>a>>b;
    for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) w[i][j] = INF;
    while(m--){
        int h1,h2,h3;
        cin>>h1>>h2>>h3;
        w[h1][h2] = h3; w[h2][h1] = h3;
        e[h1][h2] = 1; e[h2][h1] = 1;
        ans+=h3;
    }
    dijkstra(); bfs();
    cout<<ans;
    return 0;
}