解题思路

import java.util.Scanner;

public class Main{
    
    public static void main(String[] args){
        Scanner sin = new Scanner(System.in);
        int i = sin.nextInt();
        if(90 <= i && i<= 100){
            System.out.println("A");
        }else if(80 <= i && i<= 89){
            System.out.println("B");
        }
        else if(70 <= i && i<= 79){
            System.out.println("C");
        }
        else if(60 <= i && i<= 69){
            System.out.println("D");
        }
        else if(i <= 59 && i >=0 ){
            System.out.println("E");
        }else{
            System.out.println("F");
        }
    }
}