#include <vector>
#include <sstream>
#include <algorithm>
#include <fstream>
#include <list>
#include <bitset>
#include <map>
#include <istream>
#include <stack>
#include <sstream>
#include <unordered_map>
#include <set>
#include <cmath>
#include <iostream>
#include <iomanip>
#include <queue>
#include <string>

#define endl "\n"
#define all(x) x.begin(),x.end()
#define xx first
#define yy second
#define rr return 0
#define pii pair<int,int>

typedef long long ll;
typedef long double ld;

const int NMAX = 5005;
const int MMAX = 100000 + 5;
const int KMAX = 5005;

const ll INF = 1e15;

using namespace std;

int n, m, k;
int a, b;
pair<ll, ll> c[KMAX];
vector<pair<ll, ll>> g[NMAX];
ll d[NMAX][2];

void djk(int from, int ind){
    for(int i = 1;i <= n;i++){
        d[i][ind] = INF;
    }
    d[from][ind] = 0;
    set<pair<ll, ll>> st;
    st.insert({d[from][ind], from});
    while(!st.empty()){
        pair<ll, ll> v = *st.begin();
        st.erase(st.begin());
        for(int i = 0;i < g[v.yy].size();i++){
            ll to = g[v.yy][i].xx;
            ll w = g[v.yy][i].yy;
            if(d[to][ind] > (d[v.yy][ind] + w)){
                st.erase({d[to][ind], to});
                d[to][ind] = d[v.yy][ind] + w;
                st.insert({d[to][ind], to});
            }
        }
    }
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m >> k;
    cin >> a >> b;
    for(int i = 1;i <= k;i++){
        cin >> c[i].xx >> c[i].yy;
    }
    for(int i = 0;i < m;i++){
        int x, y, s;
        cin >> x >> y >> s;
        g[x].push_back({y, s});
        g[y].push_back({x, s});
    }
    djk(a, 0);
    djk(b, 1);
    ll ans = 1e15;
    for(int i = 1;i <= k;i++){
        ans = min(ans, d[c[i].xx][0] + d[c[i].xx][1] + c[i].yy);
    }
    cout << ans;
    rr;
}