#include <bits/stdc++.h>
#define INF 1e9

using namespace std;

const long long NMAX = 1e5;

vector <long long> d(NMAX , INF) , d1(NMAX , INF);
vector <vector <pair <long long , long long> > >  g(NMAX);
priority_queue<pair <long long , long long>> q , q1;
int main() {
    freopen ("INPUT.TXT" , "r" , stdin);
    freopen ("OUTPUT.TXT" , "w" , stdout);
    long long n , m , k;
    cin >> n >> m >> k;
    long long A , B;
    cin >> A >> B;
    long long v[k + 1] , c[k + 1];
    for (long long i = 1; i <= k; i++) {
        cin >> v[i] >> c[i];
    }
    for (long long i = 1; i <= m; i++) {
        long long x , y , w;
        cin >> x >> y >> w;
        g[x].push_back({y , w});
        g[y].push_back({x , w});
    }
    long long s = A;
    q.push({0 , s});
    d[s] = 0;
    while (!q.empty()) {
        long long it = q.top().second , mn = -q.top().first;
        q.pop();
        if (mn > d[it]) continue;
        for (long long j = 0; j < g[it].size(); j++) {
            long long to = g[it][j].first;
            long long len = g[it][j].second;
            if (d[it] + len < d[to]) {
                d[to] = d[it] + len;
                q.push({-d[to] , to});
            }
        }
    }
    s = B;
    q1.push({0 , s});
    d1[s] = 0;
    while (!q1.empty()) {
        long long it = q1.top().second , mn = -q1.top().first;
        q1.pop();
        if (mn > d1[it]) continue;
        for (long long j = 0; j < g[it].size(); j++) {
            long long to = g[it][j].first;
            long long len = g[it][j].second;
            if (d1[it] + len < d1[to]) {
                d1[to] = d1[it] + len;
                q1.push({-d1[to] , to});
            }
        }
    }
    long long mn = 1e18;
    for (long long i = 1; i <= k; i++) {
        mn = min(d[v[i]] + d1[v[i]] + c[i] , mn);
    }
    cout << mn;
}