include<bits/stdc++.h>

int n, m, s, e; int map[2505][2505]; void add(int a, int b, int c); void init(void); int Dijkstra(int start, int end); int main(void) {

std::scanf("%d%d%d%d", &n, &m, &s, &e);

init();
for (int i = 1, a, b, c; i <= m; i++) {
	std::scanf("%d%d%d", &a, &b, &c);
	add(a, b, c);
}
std::printf("%d", Dijkstra(s, e));

return 0;

}

void add(int a, int b, int c) {

map[a][b] = c;
map[b][a] = c;

return;

} void init(void) {

memset(map, -1, sizeof(map));
return;

} int Dijkstra(int start, int end) {

int distance[2505];
memset(distance, 0x3f3f3f3f, sizeof(distance));
distance[start] = 0;
bool viewed[2505];
memset(viewed, false, sizeof(viewed));
int p = start;
int dis = 0x3f3f3f3f;
for (int i = 1; i < n; i++) {

	for (int u = 1; u <= n; u++) {
		if (!viewed[u] && distance[u] < dis) {
			p = u;
			dis = distance[u];
		}
	}
	viewed[p] = true;
	for (int u = 1; u <= n; u++) {
		if (!viewed[u] && map[p][u] != -1 && distance[p] + map[p][u] < distance[u]) {
			distance[u] = distance[p] + map[p][u];
		}
	}
	dis = 0x3f3f3f3f;
}
return distance[end];

}