import java.util.*;
public class Main {
    static String numberToTitle(int n){
        if(n<=0) return "Invalid input";
        StringBuilder sb=new StringBuilder();
        while(n>0){
            n--;
            sb.insert(0,(char)('A'+n%26));
            n/=26;
        }
        return sb.toString();
    }
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int n=sc.hasNextInt()?sc.nextInt():-1;
        System.out.println(n>0?numberToTitle(n):"Invalid input");
    }
}