#include<bits/stdc++.h>
using namespace std;
#define PII pair<int,int>
const int N=1e5+10;
vector<PII>G[N];
int f[N],v[N],n,m,d,p,st;
int main()
{
	cin>>d>>m>>n>>p>>st;
	for(int i=1;i<=m;i++)
	{
		int x,y;cin>>x>>y;
		G[x].push_back({y,d});
	}
	for(int i=1;i<=p;i++)
	{
		int x,y,t;cin>>x>>y>>t;
		G[x].push_back({y,d-t});
	}
	deque<int>q;q.push_back(st);int ans=d;f[st]=d;
	while(!q.empty())
	{
		int x=q.front();q.pop_front();
		v[x]=0;
		if(ans>n*d)
		{
			cout<<-1;
			return 0;
		}
		for(auto i:G[x])
		{
			int y=i.first,w=i.second;
			if(f[y]<f[x]+w)
			{
				f[y]=f[x]+w;ans=max(ans,f[y]);
				if(!v[y])q.push_back(y),v[y]=1;
			}
		}
	}
	cout<<ans;
	return 0;
}