package yukicoder327;
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		char[] f={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
		
//		26characters;abcdefghijklmnopqrstuvwxyz
//26進数に変換すればいい！
		String ans="";
//		if(n==0){
//			System.out.println(f[0]);
//			System.exit(0);
//		}
		while(n>=0){
			long a=n%26;
			n=(n-a)/26-1;
			ans=f[(int)a]+ans;
		}
		System.out.println(ans);
	}
}