import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            long n = Long.parseLong(scan.next());
            String ans = "";
            boolean first = true;
            
            while(true) {
                long rem = n % 26;
                if(!first) {
                    if(rem == 0) { 
                        rem = 25;
                        n--;
                    } else {
                        rem--;
                    }
                } else {
                    first = false;
                }
                ans = (char)(rem+'A') + ans;
                long div = n / 26;
                n = div;
                if(n==0) break;   
            }
            System.out.println(ans);
        }
    }
}