#include <iostream>  
    #include <cstdio>  
    #include <cstdlib>  
    #include <cstring>  
    #include <queue>  
    using namespace std;  
    #define INF 9999999  
    #define MAXN 10240  
    struct NODE{  
        int num;  
        int nextt[MAXN],e[MAXN];  
    }p[MAXN];  
    int n,en,t;  
    bool vis[MAXN]={0};  
    int d[MAXN];  
    queue <int> q;  
    int spfa(int root){  
        for(int i=1;i<=n;i++) d[i]=(i==root)?0:INF;  
        q.push(root);  
        vis[root]=1;  
        while(!q.empty()){  
            t=q.front();  
            q.pop();  
            vis[t]=0;  
            for(int i=1;i<=p[t].num;i++){  
                if(d[p[t].nextt[i]]>d[t]+p[t].e[i]){  
                    d[p[t].nextt[i]]=d[t]+p[t].e[i];  
                    if(!vis[p[t].nextt[i]]){  
                        vis[p[t].nextt[i]]=1;  
                        q.push(p[t].nextt[i]);  
                    }  
                }  
            }  
        }  
        return d[en];  
    }  
    int main()  
    {  
        int m,beg,l,r,w;  
        scanf("%d %d %d %d",&n,&m,&beg,&en);  
        for(int i=1;i<=m;i++){  
            scanf("%d %d %d",&l,&r,&w);  
            p[l].num++;  
            p[l].nextt[p[l].num]=r;  
            p[l].e[p[l].num]=w;  
            p[r].num++;  
            p[r].nextt[p[r].num]=l;  
            p[r].e[p[r].num]=w;  
        }  
        printf("%d\n",spfa(beg));  
        return 0;  
}