#include <algorithm>
#include <iostream>
#include <cstring>
#include <vector>
#define xx first
#define yy second
using namespace std;
const int N = 2505, M = 6205;
typedef long long ll;
int n, m, s, t;
int num, h[N], to[M << 1], w[M << 1], nxt[M << 1];
inline void adde(int x, int y, int z) 
{++ num; nxt[num] = h[x]; to[num] = y; w[num] = z; h[x] = num;}
int q[N], hh, tt;
ll dis[N];
bool vis[N];
void spfa() {
	memset(dis, 0x3f, sizeof dis);
	q[tt ++] = s; dis[s] = 0; vis[s] = 1;
	while (hh != tt) {
		int x = q[hh ++];
		hh = hh == N ? 0 : hh;
		vis[x] = 0;
		for (int i = h[x]; i; i = nxt[i]) {
			const int y = to[i];
			if (dis[y] > dis[x] + w[i]) {
				dis[y] = dis[x] + w[i];
				if (!vis[y]) {
					q[tt ++] = y;
					tt = tt == N ? 0 : tt;
					vis[y] = 1;
				}
			}
		}
	}
}
signed main() {
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n >> m >> s >> t;
	for (int i = 1; i <= m; ++ i) {
		int x, y, z;
		cin >> x >> y >> z;
		adde(x, y, z); adde(y, x, z);
	}
	spfa(); cout << dis[t] << '\n';

	return 0;
}