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#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define endl "\n"
 
const double PI = 3.14159265358979;
const ll INF =  1e18 + 7;
const ll MOD = 1e9 + 7;
const ll nax = 2505;
const int LOG = 25;


void solve() {
    int n, m, q;
    cin >> n >> m >> q;

    ll dist[n][n];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            dist[i][j] = INF;
        }
        dist[i][i] = 0;
    }

    for (int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        a--;b--;
        dist[a][b] = dist[b][a] = min(dist[a][b], 1LL * c);
    }

    for (int k = 0; k < n; k++) {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
            }
        }
    }

    while(q--) {
        int a, b;
        cin >> a >> b;
        cout << (dist[a - 1][b - 1] >= INF ? -1 : dist[a - 1][b - 1]) << endl;
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    // int t; cin >> t; while(t--)
    solve();
    return 0;
}