#include <iostream> using namespace std; int main() { int score; cin >> score; if (score >= 90) { cout << "A" << endl; } else if (score >= 70) { // 隐含条件：score < 90 cout << "B" << endl; } else if (score >= 60) { // 隐含条件：score < 70 cout << "C" << endl; } else { // 隐含条件：score < 60 cout << "D" << endl; } return 0; }