//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <queue>

using namespace std;

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);
const int INF = 123456789;

int N, M, E, S, T, R;
int ea[10], eb[10], ec[10];
int dp[1<<8][8][110];
int dist[1<<8][100][100];

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  cin >> N >> M >> E >> S >> T >> R;
  fill((int*)dp, (int*)dp+(1<<8)*8*110, INF);
  fill((int*)dist, (int*)dist+(1<<8)*100*100, INF);
  REP(i,M){
	int a, b; cin >> a >> b;
	dist[0][a][b] = dist[0][b][a] = 1;
  }
  REP(i,N)
	dist[0][i][i] = 0;
  REP(i,E){
	cin >> ea[i] >> eb[i] >> ec[i];
	if(ec[i] == S)
	  dist[0][ea[i]][eb[i]] = dist[0][eb[i]][ea[i]] = 1;
  }
  REP(k,N) REP(i,N) REP(j,N)
	dist[0][i][j] = dist[0][j][i] = min(dist[0][i][j],
										dist[0][i][k]+dist[0][k][j]);

  const int MAX = 1 << E;
  REP(bi,MAX) REP(i,N) REP(j,N)
	dist[bi][i][j] = dist[0][i][j];

  REP(bi,MAX){
	REP(k,E){
	  if(bi>>k&1) continue;
	  int a = ea[k], b = eb[k];
	  dist[bi][a][b] = dist[bi][b][a] = 1;
	  REP(i,N) REP(j,N){
	  int t = min(dist[bi][i][a]+1+dist[bi][b][j],
				  dist[bi][i][b]+1+dist[bi][a][j]);
	  if(t < dist[bi][i][j])
		dist[bi][i][j] = dist[bi][j][i] = t;
	  }
	}
  }

  int ans = INF;
  if(dist[MAX-1][S][T] <= R)
	ans = dist[MAX-1][S][T];
  dp[MAX-1][0][0] = 0;
  REP(x,E){
	int bit = (MAX-1)^(1<<x);
	int r = dist[MAX-1][S][ec[x]];
	if(r <= R)
	  dp[bit][x][r] = r;
  }
  
  for(int bit=MAX-1;bit>=0;--bit){
	REP(x,E){
	  if(bit>>x&1) continue;
	  int now = ec[x];
	  REP(r, R+1){
		if(dp[bit][x][r] >= INF) continue;
		REP(i,E){
		  if(!(bit>>i&1)) continue;
		  int nxt_bit = bit ^ (1<<i);
		  int to = ec[i];
		  int nxt_r = dist[bit][now][to]+r;
		  if(nxt_r <= R){			
			dp[nxt_bit][i][nxt_r] = min(dp[nxt_bit][i][nxt_r],
										dp[bit][x][r]+dist[bit][now][to]);
		  }
		  nxt_r = dist[bit][S][to];
		  if(nxt_r <= R){
			dp[nxt_bit][i][nxt_r] = min(dp[nxt_bit][i][nxt_r],
										dp[bit][x][r]+1+nxt_r);
		  }
		}
		if(r+dist[bit][now][T] <= R)
		  ans = min(ans, dp[bit][x][r]+dist[bit][now][T]);
		if(dist[bit][S][T] <= R)
		  ans = min(ans, dp[bit][x][r]+1+dist[bit][S][T]);
	  }
	}
  }

  cout << (ans >= INF? -1: ans) << endl;
  
  return 0;
}

Measured memory_bytes: 12080