IOPC14O Wrong Answer

I got a WA on this code for this problem . I read a few accepted codes and I've done exactly the same thing in my code! Can someone point out where I'm going wrong? I'm posting a cleaner version of my submission here:

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#define ll long long

using namespace std;

ll gcd(ll a, ll b);
int check_if_powerTwo(ll n);
int isPowTwoDiff(ll n);

int main()
{
  ll T;
  cin >> T;
  while(T--){
    ll p, q;
    cin >> p >> q;
    ll greatest_factor = gcd(p,q);
    // Reduce p/q
    p = p/greatest_factor;
    q = q/greatest_factor;
    if(p >= q)
      p = p - q;  //reduce by 1

    if(p > q)
      cout << "NO" << endl;  // p/q > 2
    else if(p == q || p == 0)
      cout << "YES" << endl;  // p/q = 1 or 2
    else {
      // if p = 1: q = 2^k - 1 OR q = 2^j(2^k-1) , for some j,k
      if(p == 1) {   
    if(check_if_powerTwo(q+1) || isPowTwoDiff(q))
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
      }
      // else if p = 2^i: q = 2^k - 1
      else if(check_if_powerTwo(p)){
    if(check_if_powerTwo(q+1))
      cout << "YES"<< endl;
    else
      cout << "NO" << endl;
      }
      else
    cout << "NO" << endl;
    }
  }
  return 0;
}

ll gcd(ll a, ll b)
{
  ll rem;
  if(a > b){
    ll temp = a;
    a = b;
    b = temp;
  }
  while((rem = b % a)) {
    b = a;
    a = rem;
  }
  return a;
}

int check_if_powerTwo(ll n)
{
  if(n & (n-1))
    return 0;
  else
    return 1;
}

// is n = 2^i - 2^j
int isPowTwoDiff(ll n)
{
  if(n == 0)
    return 0;
  while(n % 2 == 0)
    n = n / 2;
  return(check_if_powerTwo(n + 1));
}