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

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int INF = 1e9;
const int N = 107;

int d[N][N];

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, m, s, t;
	cin >> n >> m >> s >> t;
	s--;
	t--;
	FOR(i, 0, n) {
		FOR(j, 0, n) {
			d[i][j] = i == j ? 0 : INF;
		}
	}
	vector<tuple<int, int, int>> edges(m);
	FOR(i, 0, m) {
		auto& [u, v, w] = edges[i];
		cin >> u >> v >> w;
		u--;
		v--;
		d[u][v] = d[v][u] = w;
	}
	FOR(k, 0, n) {
		FOR(i, 0, n) {
			FOR(j, 0, n) {
				d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
			}
		}
	}
	int ans = 0;
	for (auto [u, v, w] : edges) {
		if (min(d[s][u] + d[t][v], d[s][v] + d[t][u]) + w != d[s][t]) {
			ans += w;
		}
	}
	cout << ans << "\n";
	return 0;
}