#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <climits>
#include <ctime>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <set>
#include <map>
#include <iostream>
#include <deque>
#include <complex>
#include <string>
#include <iomanip>
#include <sstream>
#include <bitset>
#include <valarray>
#include <unordered_map>
#include <iterator>
#include <functional>
#include <cassert>
using namespace std;
typedef long long int ll;
typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;

#define REP(i,x) for(int i=0;i<(int)(x);i++)
#define REPS(i,x) for(int i=1;i<=(int)(x);i++)
#define RREP(i,x) for(int i=((int)(x)-1);i>=0;i--)
#define RREPS(i,x) for(int i=((int)(x));i>0;i--)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();i++)
#define RFOR(i,c) for(__typeof((c).rbegin())i=(c).rbegin();i!=(c).rend();i++)
#define ALL(container) (container).begin(), (container).end()
#define RALL(container) (container).rbegin(), (container).rend()
#define SZ(container) ((int)container.size())
#define mp(a,b) make_pair(a, b)
#define pb push_back
#define eb emplace_back
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"["; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"]"; return os;
}
template<class T> ostream& operator<<(ostream &os, const set<T> &t) {
os<<"{"; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"}"; return os;
}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class S, class T> pair<S,T> operator+(const pair<S,T> &s, const pair<S,T> &t){ return pair<S,T>(s.first+t.first, s.second+t.second);}
template<class S, class T> pair<S,T> operator-(const pair<S,T> &s, const pair<S,T> &t){ return pair<S,T>(s.first-t.first, s.second-t.second);}

const int INF = 1<<28;
const double EPS = 1e-8;
const int MOD = 1000000007;


int n, m, e, s, t, r, start;

int dp[1<<8][101][101];
int type[101][101], event[101];
int main(int argc, char *argv[]){
	ios::sync_with_stdio(false);
	scanf("%d%d%d%d%d%d", &n, &m, &e, &s, &t, &r);
	start = s;
	if(r == 0){
		puts("-1");
		return 0;
	}
	vector<vi> g(n);
	REP(i, m){
		int u, v;
		scanf("%d%d", &u, &v);
		g[u].pb(v);
		g[v].pb(u);
	}
	REP(i, e){
		int u, v, w;
		scanf("%d%d%d", &u, &v, &w);
		g[u].pb(v);
		g[v].pb(u);
		type[u][v] = type[v][u] = 1<<i;
		event[w] = 1<<i;
	}
	REP(i, n){
		g[i].pb(s);
		type[i][s] = 0;
	}
	
	struct State{
		int c, v, bit, r;
		State(int c, int v, int bit, int r):c(c), v(v), bit(bit), r(r){}
		bool operator<(const State &opp) const{
			return c > opp.c;
		}
	};
	
	priority_queue<State> pq;
	pq.emplace(0, s, event[s], r);
	memset(dp, 64, sizeof(dp));
	dp[event[s]][s][r] = 0;
	while(!pq.empty()){
		State s = pq.top(); pq.pop();
		if(s.v == t){
			cout << s.c << endl;
			return 0;
		}
		if(dp[s.bit][s.v][s.r] < s.c) continue;
		FOR(v, g[s.v]){
			if(type[s.v][*v] && !(type[s.v][*v] & s.bit)) continue;
			State t = s;
			t.c += 1;
			t.bit |= event[*v];
			t.r --;
			if(*v == start) t.r = r;
			if(t.r < 0) continue;
			t.v = *v;
			if(chmin(dp[t.bit][t.v][t.r], t.c)) pq.push(t);
		}
		
	}
	puts("-1");
	return 0;
}

Measured memory_bytes: 11580