#include <bits/stdc++.h>
using lint = long long;
const int N = 2507, M = 6207, E = M * 2;
const lint inf = 0x3f3f3f3f3f3f3f3f;
int n, m, s, t;
struct
{
    int v, w, nxt;
} e[E];
int head[N], tot, vis[N];
lint dis[N];
void Add(int u, int v, int w) { e[++tot] = {v, w, head[u]}, head[u] = tot; }
int main()
{
    scanf("%d%d%d%d", &n, &m, &s, &t);
    for (int i = 1; i <= m; ++i)
    {
        int u, v, w;
        scanf("%d%d%d", &u, &v, &w);
        Add(u, v, w), Add(v, u, w);
    }
    for (int i = 1; i <= n; ++i)
        dis[i] = inf;
    dis[s] = 0;
    for (int c = 1; c < n; ++c)
    {
        int u = -1;
        for (int i = 1; i <= n; ++i)
            u = vis[i] ? u : (u == -1 ? i : (dis[i] < dis[u] ? i : u));
        vis[u] = 1;
        for (int i = head[u]; i; i = e[i].nxt)
        {
            auto &x = e[i];
            dis[x.v] = std::min(dis[x.v], dis[u] + x.w);
        }
    }
    printf("%lld", dis[t]);
    return 0;
}