import java.util.ArrayList;
import java.util.Scanner;
class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long num = sc.nextLong();
		ArrayList <Character> list = new ArrayList<Character>();
		while(true) {
			list.add((char) ((num % 26) + 'A'));
			num /= 26;
			if(num == 0) break;
			num--;
		}
		for(int i = list.size() - 1 ; i >= 0 ; i--) 
			System.out.print(list.get(i));
		System.out.println("");
	}
}