A

#include <bits/stdc++.h>

using namespace std;

#define _test   int _TEST; cin>>_TEST; while(_TEST--)

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

        if(k>n || k>mx+1)
        {
            cout<<-1<<"\n";
            continue;
        }

        int x = 0;
        int ans = 0;

        for(int i=0; i<n; i++)
        {
            if(x == k)      x = mx;
            if(x > mx)      x=mx;
            if(x == k)      x--;

            ans += x;

            x++;
        }

        cout<<ans<<"\n";
    }
}