import java.net.NetworkInterface;
import java.util.*;

public class Main {
	static long gcd(long a,long b){
		return b == 0 ? a : gcd(b, a%b);
	}
	static long lcm(long a, long b){
		return a*b/gcd(a, b);
	}
	static int[] dx = {1,0,-1,0};
	static int[] dy = {0,1,0,-1};
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		long n = sc.nextLong();
		String ans = "";
		ans+=(char)((int)'A'+n%26);
		if(n<=25){
			System.out.println(ans);
			return;
		}
		if(n==26){
			System.out.println("AA");
			return;
		}
		int ind = 1;
		long unti = 26;
		while(n>=26*Math.pow(27, ind)) {ind++;unti++;}
		ind--;
		String unko="";
		for(int i=ind;i>=0;i--){
			unko+=(char)((int)'A'+(int)(n/(26*Math.pow(27, i)))+(i==ind?-1:0));
			n%=(26*Math.pow(27, i));
		}
		System.out.println(unko+ans);
	} 
}