import java.util.*;
public class Main{
	public static void main(String... args){
		Scanner scan = new Scanner(System.in);
		long n = scan.nextLong();
		if(n == 0){
			System.out.println('A');
		}else if(0 < n && n < 26){
			System.out.println((char)(n+'A'));
		}else{
			int[] res = new int[15];
			int count = 0;
			n++;
			while(0 < n){
				res[count] += n%26;
				if(res[count] == 0){
					res[count] = 26;
					n-=26;
				}
				count++;
				n/=26;
			}

			for(int i = count -1; 0 <= i; i--){
				System.out.print((char)(res[i]-1+'A'));
			}
			System.out.println();
		}

	}
}