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 C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <math.h>

#include <algorithm>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = long long;
using P = pair<int, int>;

int main() {
  ll n;
  cin >> n;

  int plc = 0;
  int cp;
  int cnt = 1;
  if (n < 27) {
    putchar('a' + n - 1);
  } else {
    while (1) {
      cp = plc;
      plc += pow(26, cnt);
      if (n > plc) {
        cp = n - plc;
        cnt++;
        break;
      }
      cnt++;
    }
    vector<int> an(cnt, 1);
    for (int i = 1; i < cnt; i++) {
      if (cp < 26) {
        an[i] = cp;
        break;
      }
      an[i] = cp - pow(26, i);
      cp -= pow(26, i);
    }
    rep(i, cnt) { putchar(an[i] - 1 + 'a'); }
  }
  return 0;
}