import java.util.*;
import java.math.*;
import java.io.*;
 
public class Main {
	static int[] ret = new int[3];
	static int[] k;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long c = sc.nextLong()+1;
		
		String ans = "";
        while(c > 0){
            c--;
            ans = (char)(c % 26 + 'A')+ans;
            c/=26;
        }
        System.out.println(ans);
	}
}