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 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long N = sc.nextLong();
		long num = 0;
		int index = 1;
		while (num < N) {
			num += Math.pow(26, index);
			index++;
		}
		int[] alp = new int[index-1];
		for (int i = index-2; -1 < i; i--) {
			for (int j = 26; -1 < j; j--) {
				if (Math.pow(26, i)*j <= N) {
					if (j == 0) {
						alp[index-2-i] = 26;
						alp[index-2-i-1]--;
						break;
					}
					alp[index-2-i] = j;
					N -= Math.pow(26, i)*j;
					break;
				}
			}
		}
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < alp.length; i++) {
			int a = alp[i];
			if (a == 0) {
				a = 26;
				alp[i+1]--;
			}
			sb.append((char) ('a'-1+a));
		}
		System.out.println(sb);
	}
}