// AVADAKEDAVRA !!!!!
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
double eps = 1e-9;

int gcd(int a,int b)
{
	if(a<b)return gcd(b,a);
	if(b==0)return a;
	return gcd(b,a%b);
}
int issqr(int x)
{
	int w = sqrt(x);
	if(w*w==x)return w;
	w++;
	if(w*w==x)return w;
	return 0;
}
class KnightOfIntegerland {
public:
	string able(int, int, int);
};
vector<pii > sums;
string KnightOfIntegerland::able(int d, int x, int y) {
	if(x<0)x=-x;
	if(y<0)y=-y;
	if( x == 0 && y == 0)return "YES";
	for(int i=0;i*i<=d;i++)
	{
		int w = d-i*i;
		if(issqr(w))
		{
			sums.push_back(pii(i,issqr(w)));
		}
	}
	vi alsteps,sparity;
	for(int i=0;i<sums.size();i++)
	{
		int x = sums[i].first, y = sums[i].second;
		int g = gcd(x,y);
		x/=g;y/=g;
		if( (y-x)& 1)
		{
			alsteps.push_back(g);
		}
		else sparity.push_back(g);
	}
	int a = 0;
	for(int i=0;i<alsteps.size();i++)
		a = gcd(a,alsteps[i]);
	for(int i=0;i<sparity.size();i++)
		a = gcd(a,2*sparity[i]);
	int b = 0;
	for(int i=0;i<sparity.size();i++)
	{
		b = gcd(b, sparity[i]);
	}
	if(a==0)return "NO";
	if( (x-y)%a != 0)return "NO";
	for(int k=0;k<a;k++)
	{
		if( (x-b*k)%a==0)return "YES";
	}
	return "NO";
}

<%:testing-code%>
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