#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <cmath>
using namespace std;
int read(){
	int x=0,f=1;char ch = getchar();
	while(ch<'0'||ch>'9'){if(ch=='-'){f=-1;}ch = getchar();}
	while(ch>='0'&&ch<='9'){x = x*10+ch-'0';ch = getchar();}
	return x*f;
}
const int N = 2e6+5;
int n,m,S,T,k;
int head[N],tote;
struct aa{
	int nxt,to,val;
}edge[N*4];
void link(int u,int v,int w){
	edge[++tote] = (aa){head[u],v,w};head[u] = tote;
}
int rk(int x,int y){
	return x+y*n;
}
struct bb{
	int u,val;
	bool operator<(const bb&x)const{
		return val>x.val;
	}
};
priority_queue<bb>q;
bool vis[N]; 
int dis[N];
void dij(){
	q.push((bb){S,0});
	for(int i=1;i<=(k+1)*n;i++){
		dis[i] = 1e9;
	}
	dis[S] = 0;
	while(!q.empty()){
		int u = q.top().u;
		q.pop();
		if(vis[u]){
			continue;
		}
		vis[u] = 1;
		for(int i=head[u];i;i=edge[i].nxt){
			int now = edge[i].to;
			if(dis[now]>dis[u]+edge[i].val){
				dis[now] = dis[u]+edge[i].val;
				q.push((bb){now,dis[now]});
			}
		}
	}
}
signed main(){
	n = read();m = read();S = read();T = read();k = read();
	while(m--){
		int u,v,w;
		u = read();v = read();w = read();
		for(int i=0;i<k;i++){
			link(rk(u,i),rk(v,i+1),0);
			link(rk(v,i),rk(u,i+1),0);
			link(rk(u,i),rk(v,i),w);
			link(rk(v,i),rk(u,i),w);
		}
		link(rk(u,k),rk(v,k),w);
		link(rk(v,k),rk(u,k),w);
	}
	dij();
//	for(int i=1;i<=n;i++){
//		for(int j=0;j<=k;j++){
//			cout<<dis[rk(i,j)]<<" ";
//		}
//		cout<<"\n";
//	}
	int ans = 1e9;
	for(int i=0;i<=k;i++){
		ans = min(ans,dis[rk(T,i)]);
	}
	cout<<ans<<"\n";
	return 0;
}