#include<cstdio>
#include<iostream>
#include<vector>
#include<queue>
#define MAX_N 1005
#define MAX_M 100005
using namespace std;
struct p{
int v,val;
friend bool operator <(const p &a,const p &b){
return a.val>b.val;//从小到大
}
};
//bool operator <(p a,p b){return a.val>b.val;}
//struct cmp1{
// bool operator ()(p a,p b){return a.val>b.val;}
//};
//priority_queue<p>c;
//priority_queue<p,vector<p>,cmp1>d; //优先队列运算符重载及构造方法
vector<struct p> map[MAX_N],rmap[MAX_N]; //邻接表表示，逆图
int n,m,a,b,t,s,k;
int h[MAX_N];
struct cmp2{
bool operator ()(p a,p b){return a.val+h[a.v]>b.val+h[b.v];}
};
void input()
{
struct p tmp;
scanf("%d %d",&n,&m);
while(m--){
scanf("%d %d %d",&a,&b,&t);
tmp.v=b;tmp.val=t;
map[a].push_back(tmp);
tmp.v=a;
rmap[b].push_back(tmp);
}
scanf("%d %d %d",&s,&t,&k);
if(s==t) k++;
}
void dijk() //优先队列实现dijkstra
{
struct p tmp;
int tu,tv,tval,tcost,i;
for(i=0;i<=n+1;i++)
h[i]=10000000;
// fill(h,h+n+1,INT_MAX);
priority_queue<p> q;
tmp.v=t;tmp.val=0;h[t]=0;
q.push(tmp);
while(!q.empty()){
tmp=q.top();tu=tmp.v;tval=tmp.val;q.pop();
if(h[tu]!=tval) continue; //顶点tu已访问过。估值函数h[]=dist[][t]
for(i=0;i<rmap[tu].size();i++){
tv=rmap[tu][i].v;tcost=rmap[tu][i].val;
if(h[tv]>tcost+tval){
tmp.v=tv;tmp.val=tcost+tval;
q.push(tmp);
h[tv]=tcost+tval;
}
}
}
}
int A_STAR()
{
struct p tmp;
int tu,tval,i;
priority_queue<p,vector<p>,cmp2>q;
int cnt[MAX_N];
memset(cnt,0,sizeof(cnt));
if(h[s]==INT_MAX) return -1;
tmp.v=s;tmp.val=0;
q.push(tmp);
while(!q.empty()){
tmp=q.top();tu=tmp.v;tval=tmp.val;q.pop();
cnt[tu]++;
if(cnt[t]==k) return tval;
if(cnt[tu]>k) continue; //如果x是s到t的第k短路径上的一个节点，那么由这条路径s到x是s到x的第m短路径，则不可能有m>k
for(i=0;i<map[tu].size();i++){
tmp.v=map[tu][i].v;tmp.val=map[tu][i].val+tval;
q.push(tmp);
}
}
return -1;
}
int main()
{
input();
dijk();
printf("%d\n",A_STAR());
return 0;
}
#include<iostream>
#include<vector>
#include<queue>
#define MAX_N 1005
#define MAX_M 100005
using namespace std;
struct p{
int v,val;
friend bool operator <(const p &a,const p &b){
return a.val>b.val;//从小到大
}
};
//bool operator <(p a,p b){return a.val>b.val;}
//struct cmp1{
// bool operator ()(p a,p b){return a.val>b.val;}
//};
//priority_queue<p>c;
//priority_queue<p,vector<p>,cmp1>d; //优先队列运算符重载及构造方法
vector<struct p> map[MAX_N],rmap[MAX_N]; //邻接表表示，逆图
int n,m,a,b,t,s,k;
int h[MAX_N];
struct cmp2{
bool operator ()(p a,p b){return a.val+h[a.v]>b.val+h[b.v];}
};
void input()
{
struct p tmp;
scanf("%d %d",&n,&m);
while(m--){
scanf("%d %d %d",&a,&b,&t);
tmp.v=b;tmp.val=t;
map[a].push_back(tmp);
tmp.v=a;
rmap[b].push_back(tmp);
}
scanf("%d %d %d",&s,&t,&k);
if(s==t) k++;
}
void dijk() //优先队列实现dijkstra
{
struct p tmp;
int tu,tv,tval,tcost,i;
for(i=0;i<=n+1;i++)
h[i]=10000000;
// fill(h,h+n+1,INT_MAX);
priority_queue<p> q;
tmp.v=t;tmp.val=0;h[t]=0;
q.push(tmp);
while(!q.empty()){
tmp=q.top();tu=tmp.v;tval=tmp.val;q.pop();
if(h[tu]!=tval) continue; //顶点tu已访问过。估值函数h[]=dist[][t]
for(i=0;i<rmap[tu].size();i++){
tv=rmap[tu][i].v;tcost=rmap[tu][i].val;
if(h[tv]>tcost+tval){
tmp.v=tv;tmp.val=tcost+tval;
q.push(tmp);
h[tv]=tcost+tval;
}
}
}
}
int A_STAR()
{
struct p tmp;
int tu,tval,i;
priority_queue<p,vector<p>,cmp2>q;
int cnt[MAX_N];
memset(cnt,0,sizeof(cnt));
if(h[s]==INT_MAX) return -1;
tmp.v=s;tmp.val=0;
q.push(tmp);
while(!q.empty()){
tmp=q.top();tu=tmp.v;tval=tmp.val;q.pop();
cnt[tu]++;
if(cnt[t]==k) return tval;
if(cnt[tu]>k) continue; //如果x是s到t的第k短路径上的一个节点，那么由这条路径s到x是s到x的第m短路径，则不可能有m>k
for(i=0;i<map[tu].size();i++){
tmp.v=map[tu][i].v;tmp.val=map[tu][i].val+tval;
q.push(tmp);
}
}
return -1;
}
int main()
{
input();
dijk();
printf("%d\n",A_STAR());
return 0;
}
