#include <bits/stdc++.h>
using namespace std;
const int N = 2510;
const int M = 6200 * 2 + 10;

typedef pair<int, int> PII;

int h[N], w[M], e[M], ne[M], idx;
bool st[N];
int dis[N];

void add(int a, int b, int c) {
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}

int n, m, S, T;

int dijkstra() {
    memset(dis, 0x3f, sizeof dis);
    dis[S] = 0;

    priority_queue<PII, vector<PII>, greater<PII>> q;
    q.push({0, S});
    while (q.size()) {
        PII t = q.top();
        q.pop();
        int u = t.second;
        if (st[u]) continue;
        st[u] = true;
        for (int i = h[u]; ~i; i = ne[i]) {
            int v = e[i];
            if (dis[v] > dis[u] + w[i]) {
                dis[v] = dis[u] + w[i];
                q.push({dis[v], v});
            }
        }
    }
    return dis[T];
}

int main() {
    cin >> n >> m >> S >> T;
    memset(h, -1, sizeof h);

    while (m--) {
        int a, b, c;
        cin >> a >> b >> c;
        add(a, b, c), add(b, a, c);
    }
    printf("%d\n", dijkstra());
    return 0;
}