#include <iostream>
#include <algorithm>
#include <stack>
#include <ctype.h>

int main(){
	std::stack<int> balls;
	int n, current_ball, extracted_ball;
	bool cheater;

	std::cin >> n;

	current_ball = 1;
	while(n){
		std::cin >> extracted_ball;
		std::cout << "inside cycle" << std::endl;
		while(true){
			balls.push(current_ball);
			std::cout << "while true" << std::endl;
			std::cout << "extracted = " << extracted_ball << std::endl;
			std::cout << "current = " << current_ball << std::endl;
			if(current_ball == extracted_ball){
				std::cout << "stop: " << (current_ball == extracted_ball) << std::endl;
				balls.pop();
				break;
			}
			current_ball++;
			if(current_ball == 50) break;
		}
		n--;	//Условие остановки - просмотрели всю последовательность
	}
	if(balls.empty())
		std::cout << "Not a proof" << std::endl;
	else
		std::cout << "Cheater" << std::endl;

	int pause;
	std::cin >> pause;
}