#include <fstream>
#include <vector>
#include <iostream>
using namespace std;


int main()
{
    int n, m, q;
    
    cin>>n>>m>>q;
    
    long long a, b, c;
    
    long long shortestpath[n][n];
    
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            shortestpath[i][j]=1e18;
        }
        shortestpath[i][i] = 0;
    }

    for(int j=0; j<m; j++){
    cin>>a>>b>>c;
        a--;
        b--;
    shortestpath[a][b]=min(shortestpath[a][b], c);
        shortestpath[b][a] = min(shortestpath[a][b], c);
    }


    for(int k=0; k<n; k++){
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
               if((shortestpath[j][k]!=1e18)and(shortestpath[i][k]!=1e18))
                if((i!=k)and(j!=k) and i != j and(shortestpath[i][k]+shortestpath[j][k]<shortestpath[i][j])){
                    shortestpath[i][j]=shortestpath[i][k]+shortestpath[j][k];
                }
            }
        }
    }

        for(int j=0; j<q; j++){
            int a,b;
            cin>>a>>b;
            a--; b--;
            if(shortestpath[a][b] == 1e18) {
                cout << -1 << endl;
            }
      else  cout<<shortestpath[a][b]<<" "<<endl;
        }


    return 0;
}