#include<iostream>#include<algorithm>#include<cstdio>#include<cstdlib>#include<queue>#include<vector>#include<cstring>#include<cmath>#include<map>using namespace std;typedef long long ll;#define N 2011111struct PP{    int v,w;}tem;vector<PP>q[1111];queue<int>p;int b[1111];int main(){    int n,m,s,t;    cin>>n>>m>>s>>t;    for(int i=1;i<=n;i++)b[i]=-1;    while(m--){        int u,v,w;        cin>>u>>v>>w;        tem.v=v;        tem.w=w;        q[u].push_back(tem);        tem.v=u;        q[v].push_back(tem);    }    b[s]=0;    p.push(s);    while(!p.empty()){        int u=p.front();        p.pop();        for(int i=0;i<q[u].size();i++){            int v=q[u][i].v,w=q[u][i].w;            if(b[v]==-1||b[v]>b[u]+w){                b[v]=b[u]+w;                p.push(v);            }        }    }    cout<<b[t]<<endl;    return 0;}