B

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)
#define ff     first
#define ss     second
#define pb     push_back
#define ppb    pop_back

int main()
{
    _test
    {
        ll int n, k, g;
        cin>>n>>k>>g;

        ll int save = min((n-1)*((g-1)/2), k*g);
        ll int rem = k*g - save;
        ll int r = rem%g;

        if(2*r >= g)        save -= (g-r);
        else                save += r;

        cout<<save<<"\n";
    }
}