https://codeiq.jp/q/2628

SquareQuartet.cs

using System;
using System.Collections;
using System.Collections.Generic;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		// (x+y)(x-y)=(B-A)(B+A)=Z として、Zの約数から(x､y)が解けるものを選ぶ
		long Z=(B-A)*(B+A);
		long ans=0;
		for(long i=1;i*i<=Z;i++){
			if(Z%i!=0)continue;
			if(i*i==Z)continue;// case: (X+Y)==(X-Y) => Y==0 is not Natural Number;
			if((i+Z/i)%2==0)ans+=Z/i;
		}
		Console.WriteLine(ans);
	}
	
	long A,B;
	public Sol(){
		var d=rla();
		A=d[0];B=d[1];
	}
	
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
}