import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        if(!sc.hasNextInt()){
            System.out.println("Invalid input");
            return;
        }
        int n=sc.nextInt();
        if(n<=0){
            System.out.println("Invalid input");
            return;
            
        }
        StringBuilder result=new StringBuilder();
        while(n>0)
        {
            n--;
            int rem=n%26;
            result.append((char)('A'+rem));
            n/=26;
        }
            System.out.println(result.reverse().toString());
            }
    }