C :

#include<stdio.h>   

int main(){ 
	int a;
	
	scanf("%d",&a);
	
	if(a < 10){
		printf("A");
	}else if(a >= 10 && a < 20){
		printf("B");
	}else if(a >= 20 && a < 40){
		printf("C");
	}else if(a >= 40 && a < 50){
		printf("D");
	}else if(a >= 50 && a < 80){
		printf("E");
	}

	return 0;
} 

C++ :

#include<iostream>
#include<iomanip>
using namespace std;
int main(){
	int n;
	cin>>n;
	if(n<10){
	cout<<"A"<<endl;
}else if(n>=10&&n<20){
	cout<<"B"<<endl;
}else if(n>=20&&n<40){
	cout<<"C"<<endl;
}else if(n>=40&&n<50){
	cout<<"D"<<endl;
}else if(n>=50&&n<80){
	cout<<"E"<<endl;
}


	}

Pascal :

var n:longint;
begin
  read(n);
  if n<10 then writeln('A');
  if (n>=10)and(n<20) then writeln('B');
  if (n>=20)and(n<40) then writeln('C');
  if (n>=40)and(n<50) then writeln('D');
  if (n>=50)and(n<80) then writeln('E');
end.

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		@SuppressWarnings("resource")
		Scanner scanner=new Scanner(System.in);
		 int m=scanner.nextInt();
		 if (m<10)
		System.out.printf("A");
		 if (m<20&&m>=10)
				System.out.printf("B");
		 if (m<40&&m>=20)
				System.out.printf("C");
		 if (m<50&&m>=40)
				System.out.printf("D");
		 if (m<80&&m>=50)
				System.out.printf("E");
		 
		}
}

Python :

a = int(input()) 
if a<10:
    print('A')
elif a<20:
    print('B')
elif a<40:
    print('C')
elif a<50:
    print('D')
elif a<80:
    print('E')