use proconio::input;

fn divisors(n: usize) -> Vec<usize> {
	let mut ds = vec![];
	let mut k = 1;
	while k * k < n {
		if n % k == 0 {
			ds.push(k);
			ds.push(n / k);
		}
		k += 1;	
	}
	if k * k == n {
		ds.push(k);
	}
	ds
}

fn main() {
	input!(T: usize);
	for _ in 0 .. T {
		input!(A: usize, B: usize);
		if let Some(ans) = divisors(B - A).into_iter().filter_map(|d| if B >= A * (d + 1) { Some((B - A * (d + 1)) / d) } else { None } ).min() {
			println!("{ans}");
		} else {
			println!("-1");
		}
	}
}