#include <bits/stdc++.h>
using namespace std;

const int N = 110, M = N * N;

int n, m, s, t;
int hed[N], to[M], nxt[M], wt[M], edcnt;
inline void ADD(int x, int y, int z) {
    nxt[++edcnt] = hed[x];
    hed[x] = edcnt;
    to[edcnt] = y;
    wt[edcnt] = z;
}

int ans = 0;
int dis[N], vis[N];

int colored[M];

int curdis = 0;
int onpath[M], pathcnt = 0;
void dfs(int x) {
    if (x == t) {
        if (curdis == dis[t]) {
            for (int i = 1; i <= pathcnt; ++i) {
                if (!colored[onpath[i]]) {
                    colored[onpath[i]] = 1;
                    if (onpath[i] % 2 == 0) colored[onpath[i] - 1] = 1;
                    else colored[onpath[i] + 1] = 1;

                    ans -= 2 * wt[onpath[i]];
                }
            }
        }
        return;
    }

    vis[x] = 1;
    for (int i = hed[x]; i; i = nxt[i]) {
        int y = to[i];
        if (vis[y]) continue;
        onpath[++pathcnt] = i;
        curdis += wt[i];
        dfs(y);
        curdis -= wt[i];
        --pathcnt;
    }
    vis[x] = 0;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n >> m >> s >> t;
    for (int i = 1; i <= m; ++i) {
        int x, y, z;
        cin >> x >> y >> z;
        ADD(x, y, z);
        ADD(y, x, z);
    }

    priority_queue<pair<int, int>> q;
    q.emplace(0, s);
    fill(dis + 1, dis + n + 1, INT_MAX);

    while (!q.empty()) {
        auto [d, u] = q.top();
        q.pop();
        d = -d;
        if (vis[u]) continue;
        vis[u] = 1;
        dis[u] = d;
        for (int e = hed[u]; e; e = nxt[e]) {
            int v = to[e];
            if (dis[v] > dis[u] + wt[e]) {
                q.emplace(-(dis[u] + wt[e]), v);
            }
        }
    }

    for (int i = 1; i <= edcnt; ++i) {
        ans += wt[i];
    }

    fill(vis + 1, vis + n + 1, 0);
    dfs(s);



    cout << ans /  2 << '\n';
    return 0;
}