import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();
        long x;
        long y;
        char[] out = new char[11];  // 1000000000000001 <= 26^10とちょっとくらい？なので11桁

        for (int i = 0; i < 11; i++) {
            N = N - 1;  // 
            x = N / 26;
            y = N % 26;
            out[i] = (char) ('a' + y);
            if (x == 0) {
                break;
            }
            N = x;
        }

        for (int i = 10; i >= 0; i--) {
            if (out[i] == Character.MIN_VALUE) {
                continue;
            }
            System.out.print(out[i]);
        }
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz