import java.util.Scanner;

public class Main {

	static long mod = 1000000007;
	static long INF = Long.MAX_VALUE;

	static long chmin(long a, long b) {
		return Math.min(a, b);
	}

	static long chmax(long a, long b) {
		return Math.max(a, b);
	}

	public static void main(String[] args) {
		// AtCoder_C
		Scanner sc = new Scanner(System.in);
		long N = sc.nextLong();
	    // Scannerクラスのインスタンスをクローズ
		sc.close();

		String ans = "";

		while (N>0) {
			N -= 1;
			ans = (char)('a'+(N%26)) + ans;
			N /= 26;
		}

		System.out.print(ans);
	}
}
/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