Atcoder problem

I tried to solve this question asked at atcoder but didn’t succeed, please help me how to solve questions like this
problem link:-


#include <bits/stdc++.h>
using namespace std;

int main() {
	int x, y;
	cin >> x >> y;
	if(y%2 == 0)
		if(y >= 2*x && y <= 4*x) cout << "Yes\n";
		else cout << "No\n";
	else cout << "No\n";
	return 0;


It is a problem of linear equations in two variables. Let the number of cranes be A and the number of turtles be B, then A+B = X and 2A+4B = Y. On solving these we get A = 2X-(Y/2) and B = (Y/2)-X. Since A and B must be non-negative integers we get the conditions as 2 divides Y and 2X<=Y<=4X.

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thanks very much