#include <bits/stdc++.h>
using namespace std;

// Define Template          Python++
// Data Structure and Algorithm
#pragma region
#define all(vec)            (vec).begin(),(vec).end()
#define sortvec(vec)        sort(all(vec));
#define minvec(vec)         *min_element(all(vec))
#define maxvec(vec)         *max_element(all(vec))
#define uma(var,val)        var=max(var,(val));
#define umi(var,val)        var=min(var,(val));
#define sumvec(vec)         accumulate(all(vec),0LL)
#define reversevec(vec)     reverse(all(vec));
#define range(i,s,e)        for(int i=s;i<e;i++)
#define range2(i,s,e)       for(int i=s;i>=e;i--)
#define fors(var,arr)       for(auto &var:arr)
// Input Output Manage
#define debug(x)            cout<<(#x)<<" : "<<(x)<<endl;
#define test                cout<<"test"<<endl;
#define fastIO              ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define floatprecision      cout<<fixed<<setprecision(6);
#define fileread            freopen("input.txt","r",stdin);
#define fileout             freopen("output.txt","w",stdout);
#define query               cin>>QUERY;while(QUERY--)
#define inputvec(vec,am)    vector<int> vec(am);fors(num,vec)cin>>num;
#define inputmat(mat,n,m)   vector<vector<int>> mat(n, vector<int>(m, 0));range(i,0,n)range(j,0,m)cin>>mat[i][j];
#define input(var)          int var;cin>>var;
#define input2(a,b)         int a,b;cin>>a>>b;
#define inputp(var)         pair<int,int> var;cin>>var.first>>var.second;
#define inputs(var)         string var;cin>>var;
#define print(var)          cout<<(var)<<endl;
#define prints(var)         cout<<(var)<<" ";
#define print2(var1,var2)   cout<<(var1)<<" "<<(var2)<<endl;
#define printp(paired)      cout<<(paired.first)<<" "<<(paired.second)<<endl;
#define printyes(cond)      cout<<((cond)?"YES":"NO")<<endl;
#define printarr(arr)       fors(num,arr){cout<<num<<" ";};cout<<endl;
#define endline             cout<<endl;
#pragma endregion
// Macro
#pragma region
#define ll    long long
#define pb    push_back
#define pq    priority_queue
#define mp    make_pair
#define vi    vector<int>
#define pii   pair<int,int>
#define vpii  vector<pii>
#define vvi   vector<vector<int>>
#define mii   map<int,int>
// Oneliner Function
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll sigma(ll num){return num*(num+1)/2;}
ll gcd(ll a, ll b){return (a==0?b:gcd(b%a,a));}
ll lcm(ll a, ll b){return (a*b)/gcd(a,b);}
ll binpow(ll a,ll b,ll m=INT64_MAX){ll r=1;a%=m;while(b){if(b&1)r=(r*a)%m;a=(a*a)%m;b>>=1;}return r;}
ll invmod(ll a,ll m){return gcd(a,m)==1?binpow(a,m-2,m):0;}
ll random(ll l){return rng()%(l+1);}
ll random(ll a,ll b){ll w=b-a;return a+random(w);}
#pragma endregion
// More Macro
#pragma region
#define i32   int32_t
#define int   long long
#define float long double
int QUERY;
#pragma endregion
// Constant
const int MOD = 1e9+7;
const int MOD2 = 998244353;
const long long INF = 1e18;
const int maxn = 2e5+5;



int32_t main() {
    fastIO

    input2(m, n)
    input(k)
    input2(s, t)

    vector<tuple<int, int, int>> adj[n];
    pii edges[m];
    range(i,0,m) {
        input2(u, v)
        input(w)
        adj[u].emplace_back(v, w, i);
        edges[i] = {u, v};
    }

    vector<int> dist(m, INF); // dist ended with this edge
    bool visited[m] = {};

    set<tuple<int, int, int>> forbid;
    range(i,0,k) {
        input(a)
        input(b)
        input(c)
        forbid.insert({a, b, c});
    }
    
    // void dijkstra(int node) {
    // Time Complexity : O(n + m log(m))
    priority_queue<pair<int,int>> q;
    fors(edge, adj[s]) {
        int nxt, weight, idx;
        tie(nxt, weight, idx) = edge;
        
        dist[idx] = weight;
        q.push({-weight, idx});
    }

    while(!q.empty()){
        int cidx = q.top().second;q.pop();
        if(visited[cidx])continue;
        visited[cidx] = true;

        int a = edges[cidx].first;
        int b = edges[cidx].second;

        for(auto edge:adj[b]){
            int nxt, weight, nidx;
            tie(nxt, weight, nidx) = edge;

            tuple<int, int, int> path3 = {a, b, nxt};
            if (forbid.count(path3)) continue;

            if(dist[cidx] + weight < dist[nidx]){
                dist[nidx] = dist[cidx] + weight;
                q.push({-dist[nidx], nidx});
            }
        }
    }


    int ans = INF;
    fors(edge, adj[t]) {
        int idx = get<2>(edge);
    }

    range(i,0,m) {
        if (edges[i].second == t) {
            umi(ans, dist[i])
        }
    }

    if (ans == INF) ans = -1;
    if (s == t) ans = 0;

    // range(i,0,m) {
    //     prints(edges[i].first)
    //     prints(edges[i].second)
    //     print(dist[i])
    // }

    print(ans)
    


    return 0;
}