import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		if (n < 26) {
		    System.out.println((char)(n + 'A'));
		    return;
		}
		StringBuilder sb = new StringBuilder();
		while (n > 0) {
		    char c;
		    if (n < 26) {
		        c = (char)(n % 26 + 'A' - 1);
		    } else {
		        c = (char)(n % 26 + 'A');
		    }
		    sb.insert(0, c);
		    n /= 26;
		}
		System.out.println(sb);
	}
}