// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;
int n,m,x,y,disx[30005],a,b,d;
vector<pair<int,int>> v[30005];
priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> pq;
void dijsx( )
{
    pq.push({0,x});
    disx[x]=0;
    while(!pq.empty())
    {
        int dis=pq.top().first;
        int node=pq.top().second;
        
        pq.pop();
        for(int i=0;i<v[node].size();i++)
        {
            int vecin=v[node][i].first;
            int drum=v[node][i].second;
            if(vecin>node)
            {
                
                
                if(abs(dis+drum)<abs(disx[vecin]))
                {
                    
                    disx[vecin]=dis+drum;
                    pq.push({dis+drum,vecin});
                }
            }
            else {
                
                
                if(abs(dis-drum)<abs(disx[vecin]))
                {
                    
                    disx[vecin]=dis-drum;
                     pq.push({dis-drum,vecin});
                }

            }
        }
    }
}

int main() {
    ifstream cin("sate.in");
    ofstream cout("sate.out");
	cin>>n>>m>>x>>y;
    for(int i=1;i<=m;i++)
    {
        cin>>a>>b>>d;
        v[a].push_back({b,d});
        v[b].push_back({a,d});
    }
    for(int i=1;i<=n;i++)
    disx[i]=disy[i]=1e9;
if(x>y)
swap(x,y);
dijsx( );
cout<<disx[y];

}