import java.util.ArrayList;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long N = scan.nextLong();
		scan.close();
		
		if(N < 26) {
			System.out.println((char)(N+'A'));
		} else {
			ArrayList<Long> list = new ArrayList();
			long value = N;
			while(true) {
				long tmp1 = value / 26;
				long tmp2 = value % 26;
				list.add(tmp2);
				if(tmp1 <= 26) {
					list.add(tmp1);
					break;
				}
				value = tmp1;
			}
			
			int n = list.size();
			String out = "";
			for(int i=0; i<n; i++) {
				long v = list.get(i);
				if(i>0) {
					v--;
					if(v==-1) {
						v=25L;
						if(i<n-1) {
							long v2 = list.get(i+1);
							list.set(i+1, v2-1);
						}
					}
				}
				out = (char)(v+'A') + out;
			}
			System.out.println(out);
		}
	}
}