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#include <bits/stdc++.h>
using namespace std;
/*
(朴素dijkstra) O(n2)
*/
const int N = 2510;
const int M = 6200 * 2 + 10;
int n; // n个城镇
int m; // m条路径
int S; //起点
int T; //终点
//邻接表
int h[N], w[M], e[M], ne[M], idx;
bool st[N]; //是否使用过
int dist[N]; //最短距离数组
//维护邻接表
void add(int a, int b, int c) {
e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}
int dijkstra() {
memset(dist, 0x3f, sizeof dist); //初始化为无穷大
dist[S] = 0; //出发点的距离初始化为0
for (int i = 0; i < n; i++) {
//找到距离出发点最近的点
int t = -1;
for (int j = 1; j <= n; j++)
if (!st[j] && (t == -1 || dist[j] < dist[t]))
t = j;
st[t] = true;
for (int j = h[t]; ~j; j = ne[j]) {
int k = e[j];
dist[k] = min(dist[k], dist[t] + w[j]);
}
}
return dist[T];
}
int main() {
cin >> n >> m >> S >> T;
memset(h, -1, sizeof h);
for (int i = 1; i <= m; i++) {
int a, b, c;
cin >> a >> b >> c;
add(a, b, c), add(b, a, c);
}
cout << dijkstra() << endl;
return 0;
}