#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
int n,m,k,u,v,value,s,t;
struct edge{
    int to,cost;
};
vector<edge> G[N];
int dis[N];
bool vis[N];
priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> q;
void dijkstra(){
    memset(dis,0x3f,sizeof(dis));
    dis[s]=0;
    q.push({0,s});
    while(q.size()){
        int u=q.top().second;
        q.pop();
        if(vis[u]) continue;
        vis[u]=1;
        for(auto it:G[u]){
            int v=it.to;
            int num=it.cost;
            if(dis[v]>dis[u]+num){
                dis[v]=dis[u]+num;
                q.push({dis[v],v});
            }
        }
    }
    return ;
}
int main(){
    ios::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
    cin>>n>>m>>k;
    cin>>s>>t;
    for(int i=1;i<=m;i++){
        cin>>u>>v>>value;
        G[u].push_back({v,value});
        G[v].push_back({u,value});
        for(int j=1;j<=k;j++){
            G[u+(j-1)*n].push_back({v+j*n,0});
            G[v+(j-1)*n].push_back({u+j*n,0});
            G[u+j*n].push_back({v+j*n,value});
            G[v+j*n].push_back({u+j*n,value});
        }
    }
    for(int i=1;i<=k;i++){
        G[t+(i-1)*n].push_back({t+i*n,0});
    }
    dijkstra();
    cout<<dis[t+k*n];
    return 0;
}