#include <bits/stdc++.h>

using namespace std;
const int INF = 0x3f3f3f3f;
const int N = 2510;          //结点数
const int M = 6200 * 2 + 10; //边数

struct Edge {
    int a, b, c;
} edges[M];

int n, m; // n个结点，m条边
int s, t; //起点，终点
int d[N]; //距离数组

void bellman_ford(int start) {
    memset(d, 0x3f, sizeof d);
    d[start] = 0;
    int T = n - 1;
    while (T--) {
        for (int i = 0; i < 2 * m; i++) {
            auto j = edges[i];
            d[j.b] = min(d[j.b], d[j.a] + j.c);
        }
    }
}

int main() {
    cin >> n >> m >> s >> t;
    for (int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        edges[i] = {a, b, c}, edges[m + i] = {b, a, c};
    }
    bellman_ford(s);

    cout << d[t] << endl;
    return 0;
}