#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
#include <fstream>
#include <bitset>

using namespace std;

#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
template <typename T> void print_container(ostream& os, const T& c) { const char* _s = " "; if (!c.empty()) { __typeof__(c.begin()) last = --c.end(); foreach (it, c) { os << *it; if (it != last) os << _s; } } }
template <typename T> ostream& operator<<(ostream& os, const vector<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const set<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const multiset<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const deque<T>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) { os << "(" << p.first << ", " << p.second << ")"; return os; }

template <typename T> void print(T a, int n, const string& split = " ") { for (int i = 0; i < n; i++) { cout << a[i]; if (i + 1 != n) cout << split; } cout << endl; }
template <typename T> void print2d(T a, int w, int h, int width = -1, int br = 0) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) { if (width != -1) cout.width(width); cout << a[i][j] << ' '; } cout << endl; } while (br--) cout << endl; }
template <typename T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
#define dump(v) (cerr << #v << ": " << v << endl)

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define clr(a, x) memset(a, x, sizeof(a))
#define sz(a) ((int)(a).size())
#define mp(a, b) make_pair(a, b)
#define ten(n) ((long long)(1e##n))

template <typename T, typename U> void upmin(T& a, const U& b) { a = min<T>(a, b); }
template <typename T, typename U> void upmax(T& a, const U& b) { a = max<T>(a, b); }
template <typename T> void uniq(T& a) { sort(a.begin(), a.end()); a.erase(unique(a.begin(), a.end()), a.end()); }
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
template <class T> T to_T(const string& s) { istringstream is(s); T res; is >> res; return res; }
void fast_io() { cin.tie(0); ios::sync_with_stdio(false); }
bool in_rect(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }

typedef long long ll;
typedef pair<int, int> pint;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };




int main()
{
    int n, m, e, s, t, r;
    cin >> n >> m >> e >> s >> t >> r;

    bool g[128][128];
    int eve[128][128];
    int event_id[128];
    clr(g, 0);
    clr(eve, -1);
    clr(event_id, -1);
    rep(i, m)
    {
        int a, b;
        cin >> a >> b;
        g[a][b] = g[b][a] = true;
    }
    rep(i, e)
    {
        int a, b, c;
        cin >> a >> b >> c;
        g[a][b] = g[b][a] = true;
        eve[a][b] = eve[b][a] = i;
        event_id[c] = i;
    }

    static int dp[128][128][1 << 8];
    clr(dp, -1);
    queue<tuple<int, int, int>> q;
    q.push(make_tuple(s, 0, 0));
    dp[s][0][0] = 0;
    while (!q.empty())
    {
        int u, ti, mask;
        tie(u, ti, mask) = q.front();
        q.pop();
        int d = dp[u][ti][mask] + 1;

        ++ti;
        if (event_id[u] != -1)
            mask |= 1 << event_id[u];

        if (dp[s][0][mask] == -1)
        {
            dp[s][0][mask] = d;
            q.push(make_tuple(s, 0, mask));
        }

        if (ti <= r)
        {
            rep(v, n)
            {
                if (dp[v][ti][mask] == -1 && g[u][v] && (eve[u][v] == -1 || (mask >> eve[u][v] & 1)))
                {
                    dp[v][ti][mask] = d;
                    q.push(make_tuple(v, ti, mask));
                }
            }
        }
    }

    int res = 1919810;
    erep(ti, r) rep(mask, 1 << e)
        if (dp[t][ti][mask] != -1)
            upmin(res, dp[t][ti][mask]);
    if (res == 1919810)
        res = -1;
    cout << res << endl;
}

Measured memory_bytes: 18208