import java.io.*;
public class grade{
int point
= Integer.
parseInt(in.
readLine());
if(point >= 90){
System.
out.
println("Grade: A"); }
else if(point >= 80){
System.
out.
println("Grade: B"); }
else if(point >= 70){
System.
out.
println("Grade: C"); }
else if(point >= 60){
System.
out.
println("Grade: D"); }
else{
System.
out.
println("Grade: F"); }
}
}
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