#include<bits/stdc++.h>
using namespace std;

int x, y, z;
int check(int k)
{
	if ((x + (y % k)) % k > z) {
		return 1;
	}
	else if((x + (y % k)) % k < z){
		return 2;
	}
	else {
		return 0;
	}
}

void solve()
{
	
	cin >> x >> y >> z;
	if (x + y < z) {
		cout << -1<<endl;
		return;
	}
	if (x + y == z) {
		cout << x + y + 1<<endl;
		return;
	}
	long long l = x; long long r = x + y;
	long long mid;
	while (l<r)
	{
		mid = (l + r)/2;
		//cout << "mid " << mid << endl;
		if (check(mid)==1) {
			l = mid + 1;
		}
		else if(check(mid)==2){
			r = mid - 1;
		}
		else {
			break;
		}
	}
	cout << l<<endl;
}

int main()
{
	int t;
	cin >> t;
	while (t--)
	{
		solve();
	}
	
	return 0;
}