import java.util.Scanner;

class Solution {
    public String convert(int n) {
        if (n <= 0||n.isInteger) {
            return "Invalid input";
        }

        StringBuilder result = new StringBuilder();
        while (n > 0) {
            n--;
            char c = (char) ('A' + n % 26);
            result.insert(0, c);
            n /= 26;
        }
        return result.toString();
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        System.out.println(sol.convert(a));
    }
}