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++ (Clang 10.0.0) (judge verdict: Accepted)

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <cmath>

#define rep(i, n) for(int i = 0; i < (int)n; i++)
#define reps(i, s, n) for(int i = (int)s; i < (int)n; i++)
#define in(i) std::cin >> i;
#define print(i) std::cout << i;
#define println(i) std::cout << i << std::endl;

int main() {
    long long N;
    in(N)
    N--;
    long long d;
    int i;
    for(i = 1; ; i++) {
        d = std::pow(26, i);
        if(N - d >= 0) 
            N -= d;
        else
            break;
        
    }
    std::string ans = "";
    int k = i - 1;
    for(int j = 0; j <= k; j++) {
        d = std::pow(26, i - 1);
        ans += (N / d) + 'a';
        N = N % d;
        i--;
    }
    print(ans);
    return 0;
}