import java.util.Scanner;
public class ExcelColumTitle{
    public static void main(String[] args){
        Scanner sc= new Scanner(System.in);
        String input=sc.nextLine();
        try{
            long n= Long.parseLong(input);
            if(n<=0 || n>214783647L){
                 System.out.println("Invalid input");
                    return;  
            }
            StringBuilder columnTitle=new StringBuilder();
            while(n > 0){
                n--;
                columnTitle.insert(0,(char)('A'+(n %26)));
                n/= 26;
            }
            System.out.println(columnTitle.toString());
        }
        catch(NumberFormatException e){
                 System.out.println("Invalid input");
        }
    }
}