10016 - Grading

#include <iostream>
using namespace std;

void Slove(int m, int f, int r)	{
	char result;

	if (m+f >= 80)	result='A';
	else if (m+f >= 65)	result='B';
	else if (m+f >= 50)	result='C';
	else if (m+f >= 30)	{
		result='D';
		if (r >= 50)	result='C';
	}
	else result='F';
	if (m==-1 || f==-1)	result='F';
	cout << result << endl;
}

int main(void)	{
	int m, f, r;

	cin >> m >> f >> r;
	while ( !(m==-1 && f==-1 && r==-1) )	{
		Slove(m,f,r);
		cin >> m >> f >> r;
	}
	return 0;
}

やるだけ～♪