package yuki_coder;

import java.util.Scanner;

public class No_327 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long N = sc.nextLong();
		sc.close();
		if(N==0){
			System.out.println("A");
		}else if(N < 26){
			System.out.println((char)('A' + N));
		}else if(N>=26){
			long[] ans = new long[12];
			int c = 0;
			long copy = N;
			while(copy >= 26){
				copy /= 26;
				c++;
			}
			copy = N;
			for(int i = c; i >=0; i--){
				if(i!=0){
					ans[i] = copy % 26;
					if(i != 1){
					copy /= 26;
					}
				}else if(i==0){
					ans[i] = copy / 26;
				}
			}
			for(int i = 0; i <= c; i++){
				if(i==c){
					System.out.println((char)(ans[i] + 'A'));
				}else{
					if(ans[i] != 0){
					ans[i] -= 1;
					}
					System.out.print((char)(ans[i] + 'A'));
				}
			}
		}
	}
}