C# da Fibonacci

#include <iostream> 
  #include <cmath> 
   
  using namespace std; 
   
  bool isPerfectSquare(long long num){ 
      long long x = sqrt(num); 
      return (x*x == num) ; 
  } 
   
  bool isFibonacci(long long n) 
  { 
      return isPerfectSquare(5*n*n + 4) || 
             isPerfectSquare(5*n*n - 4); 
  } 
  int main() { 
      long long N,num; 
      cin >> N; 
      for(long long i = 0 ; i < N ; i++){ 
          cin  >> num; 
          isFibonacci(num) ? cout << "IsFibo" : cout << "IsNotFibo" ; 
          cout << endl; 
      } 
      return 0 ; 
  }