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#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
#define fo(i, n) for (i = 0; i < n; i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define m_p make_pair
const ll mod=1e9+7;
#define INF LLONG_MAX
//---------------------------------------------------------------------------------------------

//---------------------------------------------------------------------------------------------
void greninja(vector<vector<pair<ll,ll>>> &graph, ll sz , ll src , vector<ll>& dist) {

    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq;
    for(auto &x:dist)
        x = INF;
    pq.push({0, src});
    dist[src] = 0;

    while (!pq.empty()) {
        ll u = pq.top().second;
        ll current_dist = pq.top().first;
        pq.pop();

        // Prune the node if the current distance is not better
        if (current_dist > dist[u]) {
            continue;
        }

        for (auto &x : graph[u]) {
            ll v = x.first;
            ll weight = x.second;

            if (dist[v] > dist[u] + weight) {
                dist[v] = dist[u] + weight;
                pq.push({dist[v], v});
            }
        }
    }
}
//---------------------------------------------------------------------------------------------
void solve()
{
    ll n , m , q;
    cin >> n >> m >> q;
    vector<vector<pair<ll,ll>>> graph(n + 1);
    ll i;
    fo(i,m)
    {
        ll a , b , c;
        cin >> a >> b >> c;
        graph[a].pb({b , c});
        graph[b].pb({a , c});
    }
    vector<ll> dist(n + 1);
    ll ans[n + 1][n + 1];
    for(i = 1 ; i <= n ; i++)
    {
        greninja(graph , n + 1 , i , dist);
        for(ll j = 1 ; j <= n ; j++)
        ans[i][j] = dist[j];
    }
    while(q--)
    {
        ll a , b;
        cin >> a >> b;
        if(ans[a][b] == INF)
        cout << -1;
        else   
        cout << ans[a][b];
        cout << "\n";
    }
}
//---------------------------------------------------------------------------------------------
 int main()
{ 
    //BINARY SEARCH ON ANS
    //DISJOINT SET UNION
    //INVERSE MODULO
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    ll t;
    // cin>>t;
    t=1;
    while(t--)
    {
        solve();
    }
}
//---------------------------------------------------------------------------------------------