#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#define ll long long
using namespace std;
const int N=1e4+5,M=5e4+5,K=15;
int n,m,k,head[N*K],xnt,s,t;
ll dis[N*K],ans=0x7fffffff;
bool vis[N*K];
struct Edge{int next,to,w;Edge(int n=0,int t=0,int w=0):next(n),to(t),w(w) {}
}edge[M*K<<2];
void add(int x,int y,int z)
{for(int fx=0;fx<=k*n;fx+=n){edge[++xnt]=Edge(head[x+fx],y+fx,z);head[x+fx]=xnt;if(fx<k*n)edge[++xnt]=Edge(head[x+fx],y+fx+n,0),head[x+fx]=xnt;}
}
void dj()
{memset(dis,1,sizeof dis);dis[s]=0;priority_queue<pair<ll,int>,vector<pair<ll,int> >,greater<pair<ll,int> > > q;q.push(make_pair(0,s));while(q.size()){int u=q.top().second;q.pop();while(vis[u]&&q.size())u=q.top().second,q.pop();if(vis[u])break;vis[u]=1;for(int i=head[u],v;i;i=edge[i].next)if(dis[v=edge[i].to]>dis[u]+edge[i].w){dis[v]=dis[u]+edge[i].w;q.push(make_pair(dis[v],v));}}
}
int main()
{scanf("%d%d%d%d%d",&n,&m,&k,&s,&t);int x,y,z;for(int i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&z);add(x,y,z);add(y,x,z);}dj();for(int fx=0;fx<=k*n;fx+=n)ans=min(ans,dis[t+fx]);printf("%lld",ans);return 0;
}

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#define ll long long
using namespace std;
const int N=1e4+5,M=5e4+5,K=15;
int n,m,k,s,t,head[N],xnt;
ll ans=0x7fffffff,dp[N][K];
bool vis[N][K];
struct Edge{int next,to,w;Edge(int n=0,int t=0,int w=0):next(n),to(t),w(w) {}
}edge[M<<1];
void add(int x,int y,int z)
{edge[++xnt]=Edge(head[x],y,z);head[x]=xnt;edge[++xnt]=Edge(head[y],x,z);head[y]=xnt;
}
void spfa()
{memset(dp,1,sizeof dp);dp[s][0]=0;queue<pair<int,int> > q;q.push(make_pair(s,0));vis[s][0]=1;while(q.size()){int u=q.front().first,d=q.front().second;q.pop();vis[u][d]=0;for(int i=head[u],v;i;i=edge[i].next){if(dp[v=edge[i].to][d]>dp[u][d]+edge[i].w){dp[v][d]=dp[u][d]+edge[i].w;if(!vis[v][d])vis[v][d]=1,q.push(make_pair(v,d));}if(d<k&&dp[v][d+1]>dp[u][d]){dp[v][d+1]=dp[u][d];if(!vis[v][d+1])vis[v][d+1]=1,q.push(make_pair(v,d+1));}}}
}
int main()
{scanf("%d%d%d%d%d",&n,&m,&k,&s,&t);int x,y,z;for(int i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&z);add(x,y,z);}spfa();for(int i=0;i<=k;i++)ans=min(ans,dp[t][i]);printf("%lld",ans);return 0;
}