백준 9498 c++

#include <iostream>
using namespace std;

int main(void)
{
	int score;

	cin >> score;

	if (score >= 0 && score <= 100)
	{
		if (score >= 90 && score <= 100)
		{
			cout << "A" << endl;
		}
		else if (score >= 80 && score <= 89)
		{
			cout << "B" << endl;
		}
		else if (score >= 70 && score <= 79)
		{
			cout << "C" << endl;
		}
		else if (score >= 60 && score <= 69)
		{
			cout << "D" << endl;
		}
		else
		{
			cout << "F" << endl;
		}
	}

	return 0;
}