import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
char zf = scanner.next().charAt(0);
int x = -1;
for(char i = 'a', j = 'A'; i <= 'z' && j <= 'Z'; i++, j++) {
if(zf == i || zf == j) {
System.out.println("YES");
x = 1;
break;
}
}
if(x == -1) {
System.out.println("NO");
}
}
}