#include<cstdio>
#include<cmath>
#define N 250000000
#define ULL unsigned long long
using namespace std;
ULL n,i,x;
int main()
{
	freopen("pitagora2.in","r",stdin);
	freopen("pitagora2.out","w",stdout);
	scanf("%d",&n);
	x=n*n;
	for(i=1;i<=x*2;i++)
		if(sqrt(i*i+x)==(ULL)sqrt(i*i+x))
			if(n+i>(ULL)sqrt(i*i+x))
				break;
	if(i>N)
		printf("-1\n");
	else
		printf("%lld\n",i);
	return 0;
}