/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        long n = Long.parseLong(br.readLine());
        ArrayList<Long> pool = new ArrayList<Long>();
        while(n>0l){
            pool.add(n%26l);
            n /= 26l;
            n--;
        }
        if(n==0l){
            pool.add(0l);
        }
        Collections.reverse(pool);
        System.out.print((char)('A'+pool.get(0)));
        for(int i=1;i<pool.size();i++){
            System.out.print((char)('A'+pool.get(i)));
        }
        
    }
}