rt

over全不过，手造数据第二组不过（#16数据和#42~#46数据）

#include<bits/stdc++.h>
#define int unsigned long long
using namespace std;
signed main()
{
	int n,m,ans=1000000000000000000;
	cin>>n>>m;
	int mn=m;
	if(n<=1e6)mn=min(m,n*n);
	for(int a=1;a*a<=mn;a++)
	{
		int b;
		if(m%a)b=m/a+1;
		else b=m/a;
		if(b>n)continue;
		ans=min(ans,a*b);
	}
	cout<<((ans==1000000000000000000)?-1:ans);
	return 0;
}