// editor2
import java.util.*;
public class image{
    public static void main(String[] args){
        Scanner s=new Scanner(System.in);
       if(!s.hasNextInt()){
            System.out.println("Invalid  input");
            return;
        }
        long n=s.nextLong();
        if(n<=0){
            System.out.println("Invalid input");
            return;
        }
        System.out.println(convertTotittle(n));
    }
    public static String
    convertTotittle(int n){
        StringBuilder result=new StringBuilder();
        while(n>0){
            n--;
            char ch =(char) ('A' + (n%26));
            result.insert(0, ch);
            n/=26;
        }
        return result.toString();
    }
}