#include <iostream>
#include <vector>
using namespace std;
vector <vector<long long>> cringe(int n, vector <vector <int>>& graph, vector <vector <long long>>& price, int start_point, long long price_now, int point_now){
    graph.resize(n, vector<int> (n));
    price.resize (n, vector <long long> (n, -1));
    for (int i=0; i<n; i++){
        if (i!=point_now){
            if (graph[point_now][i]!=0 && (price[start_point][i]==-1 || price[start_point][i]>graph[point_now][i]+price_now)){
                   price[start_point][i]=graph[point_now][i]+price_now;
                   long long l=price_now;
                   int k=point_now;
                   price_now+=graph[point_now][i];
                   point_now=i;
                   cringe(n, graph, price, start_point, price_now, point_now);
                   price_now=l;
                   point_now=k;
            }
        }
    }
    return price;
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, z, t;
    cin>>n>>z>>t;
    vector <vector <int>> graph(n, vector <int> (n));
    vector <vector <long long>> price(n, vector <long long> (n, -1));
    vector <pair<int, int>> requests(t);
    for (int i=0; i<z; i++){
        int d, e, f;
        cin>>d>>e>>f;
        graph[d-1][e-1]=f;
    }
    for (int i=0; i<t; i++){
        cin>>requests[i].first>>requests[i].second;
        requests[i].first--;
        requests[i].second--;
    }
    int start_point;
    int point_now;
    long long price_now;
    for (int i=0; i<n; i++){
        start_point=i;
        point_now=i;
        price_now=0;
        cringe(n, graph, price, start_point, price_now, point_now);
    }
    for (int i=0; i<t; i++){
        if (requests[i].first==requests[i].second){
            cout<<0<<"\n";
        }else{
            cout<<price[requests[i].first][requests[i].second]<<"\n";
        }
    }
}