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

#define pb push_back
typedef pair<int, int> pii;

const int maxn = 111;

int n, m, s, t, diss[maxn], dist[maxn], head[maxn];
bool vis[maxn];

struct edge {
    int u, v, w, nxt;
} e[maxn * maxn];

void dijkstra(int* dis, int start) {
    memset(vis, 0, sizeof(vis));

    dis[start] = 0;

    priority_queue<pii, vector<pii>, greater<pii>> pq;

    pq.push({0, start});

    while (! pq.empty()) {
        auto [_, u] = pq.top();
        pq.pop();

        if (vis[u]) continue;

        vis[u] = 1;

        for (int i = head[u], v; ~i; i = e[i].nxt) {
            v = e[i].v;

            if (dis[v] > dis[u] + e[i].w) {
                dis[v] = dis[u] + e[i].w;
                pq.push({dis[v], v});
            }
        }
    }
}

int main() {
    scanf("%d%d%d%d", &n, &m, &s, &t);
    memset(head, 0xff, sizeof(head));

    memset(diss, 0x1f, sizeof(diss));
    memset(dist, 0x1f, sizeof(dist));

    int sum = 0;

    for (int i = 0, u, v, w; i < m; i++)
        scanf("%d%d%d", &u, &v, &w), sum += w, e[i << 1] = {u, v, w, head[u]}, head[u] = i << 1, e[i << 1 | 1] = {v, u, w, head[v]}, head[v] = i << 1 | 1; 

    dijkstra(diss, s), dijkstra(dist, t);

    for (int i = 0; i < m; i++) {
        auto [u, v, w, _] = e[i << 1];

        if (diss[u] + w + dist[v] == diss[t] || dist[u] + w + diss[v] == diss[t]) sum -= w;
    }

    printf("%d\n", sum);
}