import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		long rest = sc.nextLong() + 1;
		StringBuilder sb = new StringBuilder();
		do{
			rest--;
			
			sb.insert(0, ((char)('A' + (rest % 26))));
			rest /= 26;
		}while(rest > 0);
		
		System.out.print(sb.toString());
		
	}

}