// lanqiao 1121 蓝桥公园(floyd)
#include <bits/stdc++.h>
using namespace std;
#define int long long 
const int N = 4e2+10;
int d[N][N];
int inf = 2e18;
signed main(){
  // 请在此输入您的代码
  ios::sync_with_stdio(0), cin.tie(0),cout.tie(0);
  int n, m, q; cin >> n >> m >> q;
  for(int i = 1; i <= n; i++){
    for(int j = 1; j <= n; j++){
        d[i][j] = inf; // 全部初始化为最大值
    }
    d[i][i] = 0; // 到自己的距离为0
  }
  while(m--){
    int u, v, w; cin >> u >> v >> w;
    d[u][v] = min(d[u][v], w);
    d[v][u] = min(d[v][u], w);
  }
  for(int k = 1; k <= n; k++){
    for(int i = 1; i <= n; i++){
      for(int j = 1; j <= n; j++){
        d[i][j] = min(d[i][j], (d[i][k] + d[k][j]));
      }
    }
  }
  for(int i = 1; i <= q; i++){
    int st, ed; cin >> st >> ed;
    cout << ((d[st][ed] >= inf)?-1:d[st][ed]) << '\n';
  }

  return 0;
}
/* test samples -> 1 3 2
3 3 3
1 2 1
1 3 5
2 3 2
1 2
1 3
2 3
*/