C

#include <stdio.h>
#include <string.h>

#define MAXSIZE 210
#define INF 0x3f3f3f3f
#define min(a,b) ((a)<(b)?(a):(b))
int n, m, k, dist[MAXSIZE][MAXSIZE];

void init() {
    scanf("%d%d%d", &n, &m, &k);
    memset(dist, 0x3f, sizeof(dist));
    for (int i = 1; i <= n; ++i) {
        dist[i][i] = 0;
    }

    int x, y, z;
    while (m--) {
        scanf("%d%d%d", &x, &y, &z);
        dist[x][y] = min(dist[x][y], z);
    }
}

void Floyd() {
    for (int u = 1; u <= n; ++u) {
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= n; ++j) {
                if (dist[i][u] != INF && dist[u][j] != INF) {
                    dist[i][j] = min(dist[i][j], dist[i][u]+dist[u][j]);
                }
            }
        }
    }
}

int main() {
    init();
    Floyd();
    int x, y;
    while (k--) {
        scanf("%d%d", &x, &y);
        if (dist[x][y] == INF) {
            puts("impossible");
        } else {
            printf("%d\n", dist[x][y]);
        }
    }

    return 0;
}