#include<bits/stdc++.h>
#define N 100010
#define M 500010
#define INF 99999999999999999
#define ll long long
#define mem(a,b) memset(a,b,sizeof(a))
#define fsb(a,b,c) for(ll a=b;a<=c;a++)
#define fbs(a,b,c) for(ll a=b;a>=c;a--)
using namespace std;
ll l[N],n,m,cnt=0,x,y,z,s,t,g,q,head[N],d[N],vis[N];
struct edge{
 ll p,nt,l;
}a[M*2];
struct node{
 ll u,d;
};
priority_queue<node>S;
int operator <(node a,node b){
 return a.d>b.d;
}
template<typename qw>inline void rll(qw &x){
 x=0;qw f=1;char c=getchar();
 while(!isdigit(c))f=c=='-'?-1:f,c=getchar();
 while(isdigit(c))x=x*10+c-'0',c=getchar();
 x*=f;
}
inline void add(ll x,ll y,ll z){
 a[++cnt].p=y;a[cnt].nt=head[x];head[x]=cnt;a[cnt].l=z;
}
int main(){
 rll(n);rll(m);rll(s);rll(t);rll(g);rll(q);
 fsb(i,1,n){
  rll(x);rll(y);l[i]=(i==s||i==t)?(INF):((q==0?INF:(y-x)/q));
 }
 mem(head,255);
 fsb(i,1,m){
  rll(x);rll(y);rll(z);add(x,y,z);add(y,x,z);
 }
 mem(vis,0);mem(d,60);d[s]=0;S.push((node){s,0});
 while(!S.empty()){
  ll u=S.top().u;S.pop();
  if(vis[u])continue;
  vis[u]=1;
  if(d[u]>g)break;
  for(ll t=head[u];t!=-1;t=a[t].nt){
   ll v=a[t].p;
   if(vis[v]||d[u]+a[t].l>d[v]||d[u]+a[t].l>l[v])continue;
   d[v]=d[u]+a[t].l;S.push((node){v,d[v]});
  }
 }
 if(d[t]>g)puts("wtnap wa kotori no oyatsu desu!");else printf("%lld\n",d[t]);
 return 0;
}