Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in Java (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	static List<Long> alphaList = new ArrayList<>();

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		long n = scan.nextLong();

		long count = 0;

		for (int i = 1; true; i++) {

			count += Math.pow(26, i);

			if (n <= count) {
				caliculate(i, n);
				break;
			}
		}

		String[] alphaArray = "abcdefghijklmnopqrstuvwxyz".split("");

		StringBuilder builder = new StringBuilder();

		for (long number : alphaList) {

			builder.append(alphaArray[(int) number - 1]);
		}

		println(builder.toString());
	}

	public static void caliculate(int i, long count) {

		if (i == 1) {

			alphaList.add(count);

		} else {

			long number = (long) (count / Math.pow(26, i - 1));

			if (number == 27) {

				alphaList.add(number - 1);
				caliculate(i - 1, (long) (Math.pow(26, i - 1)));

			} else {

				alphaList.add(number);
				caliculate(i - 1, (long) (count % Math.pow(26, i - 1)));
			}
		}
	}

	public static void println(Object target) {
		System.out.println(target);
	}
}