#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>order_set;
typedef pair<int, int>pr;
#define all(i) i.begin() , i.end()
#define ft first
#define sn second
#define pb push_back
#define en "\n"
#define dbg cout<<"rony\n";
#define MAXN 200010
#define inf 1e18
const ll mod = 1e9 + 7;
void solve()
{
ll n, m, q;
cin >> n >> m >> q;
vector<vector<ll>> dist( n, vector<ll>(n, inf));
for (ll i = 0; i < m; i++) {
ll x, y, c;
cin >> x >> y >> c;
x--, y--;
dist[x][x] = dist[y][y] = 0;
dist[x][y] = min(dist[x][y], c);
dist[y][x] = min(dist[y][x], c);
}
for (ll k = 0; k < n; k++) {
for (ll i = 0; i < n; i++) {
for (ll j = 0; j < n; j++) {
if (dist[i][j] > dist[i][k] + dist[k][j]) {
dist[i][j] = dist[i][k] + dist[k][j];
}
}
}
}
while (q--)
{
ll x, y;
cin >> x >> y; x--, y--;
if (x == y) {
cout << 0 << en; continue;
}
if (dist[x][y] == inf) cout << -1 << en;
else cout << dist[x][y] << en;
}
}
int main()
{
IOS;
int t;
t = 1;
// cin >> t;
int c = 0;
while ( t-- )
{
//cout<<"Case "<<++c<<": ";
solve();
}
return 0;
}