using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		
		List<int> L=new List<int>();
		do{
			L.Add((int)(N%26));
			N/=26;
		}while(N>0);
		
		L.Reverse();
		L[0]--;
		if(L[0]==0){
			L.RemoveAt(0);L[0]+=25;
		}
		
		
//Console.WriteLine(String.Join(" ",L.ToArray()));
		for(int i=0;i<L.Count;i++){
			Console.Write((char)(L[i]+'A'));
		}
		Console.WriteLine();
	}
	long N;
	public Sol(){
		N=rl();
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
}