시험 성적

#include <iostream>
using namespace std;

int main(void)
{
	int score;

	score = 0;
	if (score < 0 || score>100)
		return 0;

	cin >> score;

	
	if (90 <= score && score <= 100)
		cout << "A" << '\n';
	else if (80 <= score && score <= 89)
		cout << "B" << '\n';
	else if (70 <= score && score <= 79)
		cout << "C" << '\n';
	else if (60 <= score && score <= 69)
		cout << "D" << '\n';
	else
		cout << "F" << '\n';
	return 0;
}