using System;
using System.Text;

public class Hello{
    enum Alphabet :long{A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z}
    public static int CalcDigits(long n, int dig){
        if(n < 26){
            return dig+1;
        }else{
            return CalcDigits(n/26, dig+1);
        }
    }
    public static void Main(){
        var n = long.Parse(Console.ReadLine());
        var dig = CalcDigits(n, 0);
        var builder = new StringBuilder();
        
        for(var i = 0; i < dig; i++){
            var rem = n%26;
            builder.Append((Alphabet)(rem));
            if(rem == 0){
                n = 0;
            }else{
                n /= 26;
            } 
        }
        
        var result = builder.ToString().ToCharArray();
        Array.Reverse(result);
        System.Console.WriteLine(result);
    }
}