#include<cstdio>

 #include<cstring>

 #include<iostream>

 #include<queue>

 #define pa pair<int,int>

 #define inf 0x7fffffff

 #define M 400008

 using namespace std;

 int d[M],f[M],n,m,k,s,t,cnt,head[M],next[*M],u[*M],v[*M];

 void jia(int a1,int a2,int a3)

 {

     cnt++;

     next[cnt]=head[a1];

     head[a1]=cnt;

     u[cnt]=a2;

     v[cnt]=a3;

     return;

 }

 int main()

 {

     scanf("%d%d%d",&n,&m,&k);

     scanf("%d%d",&s,&t);

     for(int i=;i<=m;i++)

       {

         int a1,a2,a3;

         scanf("%d%d%d",&a1,&a2,&a3);

         jia(a1,a2,a3);

         jia(a2,a1,a3);

         for(int j=;j<=k;j++)

           {

             jia(j*n+a1,j*n+a2,a3);

             jia(j*n+a2,j*n+a1,a3);

             jia((j-)*n+a1,j*n+a2,);

             jia((j-)*n+a2,j*n+a1,);

           }

       }

     priority_queue<pa,vector<pa>,greater<pa> >q;

     memset(d,,sizeof(d));

     q.push(make_pair(,s));

     d[s]=;

     for(;!q.empty();)

       {

         int now=q.top().second;

         q.pop();

         if(f[now])

           continue;

         f[now]=;

         for(int i=head[now];i;i=next[i])

           if(d[u[i]]>d[now]+v[i])

             {

                 d[u[i]]=d[now]+v[i];

                 q.push(make_pair(d[u[i]],u[i]));

             }

       }

     int ans=inf;

     for(int i=;i<=k;i++)

       ans=min(ans,d[i*n+t]);

     printf("%d\n",ans);

     return ;

 }