#include <iostream>
using namespace std;
 
int main() {
    float score;
 
    // รับค่าคะแนนจากผู้ใช้
    cout << "กรุณากรอกคะแนน: ";
    cin >> score;
 
    // ตรวจสอบคะแนนและแสดงเกรด
    if (score >= 80 && score <= 100) {
        cout << "เกรด: A" << endl;
    } else if (score >= 70 && score < 80) {
        cout << "เกรด: B" << endl;
    } else if (score >= 60 && score < 70) {
        cout << "เกรด: C" << endl;
    } else if (score >= 50 && score < 60) {
        cout << "เกรด: D" << endl;
    } else if (score >= 0 && score < 50) {
        cout << "เกรด: F" << endl;
    } else {
        cout << "คะแนนไม่ถูกต้อง!" << endl;
    }
 
    return 0;
}
 

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