#include <bits/stdc++.h>
using namespace std;
int dis[2501];
bool exist[2501];//标记每个点是否在queue中 
struct point
{
	int to;
	int w;
};
int n,m,s,t;
vector<point> graph[2501];

void SPFA()
{
	memset(dis, 0x3f, sizeof(dis));
    dis[s] = 0;  // 注意起 始点是s！！！
    queue<int> q;
    q.push(s);
    exist[s]=1;
	 
   	while(q.size()>0)
   	{
   		int from=q.front();
		q.pop();
		exist[from]=0;
		for(int i=0;i<graph[from].size();i++)
		{
//			for(int temp:graph[from])
				
			int to=graph[from][i].to;
			int w=graph[from][i].w;
			if(dis[from]+w<dis[to])
			{
				dis[to]=dis[from]+w;
				if(exist[to]==0)
				{
					q.push(to);
    				exist[to]=1;
				}	
			}
		}	
	}
} 

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
	
    cin >> n >> m >> s >> t;
    for (int i = 1; i <=m ; i++) {
    	int a,b,c;
        cin >> a >> b >> c;
        graph[a].push_back({b,c});
        graph[b].push_back({a,c});
    }

    SPFA(); 

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