floyd 板子

#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const int N = 210;
int g[N][N];


int main () {
    int n, m, q;
    cin >> n >> m >> q;
    int a, b, c;
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n; ++j) {
            if (i == j) g[i][j] = 0;
            else g[i][j] = inf;
        }
    }
    for (int i = 0; i < m; i ++ ) {
        cin >> a >> b >> c;
        g[a][b] = min(g[a][b], c);
    }
    for (int k = 1; k <= n; ++k) {
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= n; ++j) {
                g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
            }
        }
    }
    for (int i = 0; i < q; i ++ ) {
        cin >> a >> b;
        if (g[a][b] > inf / 2) cout << "impossible" << endl;
        else cout << g[a][b] << endl;
    }
    return 0;
}