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(){
		
		long X=26;
		long M=0;
		int keta=1;
		while(true){
			if(X>N){
				M=N;break;
			}
			N-=X;
			X*=26;
			keta++;
		}
		
		long[] A=new long[keta];
		
		for(int i=0;i<keta;i++){
			A[i]=M%26;
			M/=26;
		}
		Array.Reverse(A);
		Console.WriteLine(String.Join("",A.Select(x=>(char)('A'+x)).ToArray()));
		
		
	}
	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));}
}