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.*;
import java.io.*;
import java.math.BigDecimal;
import java.nio.file.Files;
import java.nio.charset.StandardCharsets;
//给出两个数a,b 求出[a,b]中各位数字之和能整除原数的数的个数。
public class Main {

    int mod ;
    //
    //int[][] dp = new int[1001][1001];
    void solve(long n) {
        long[] fact = new long[17];
        long[] dp = new long[17];
        fact[1] = 26;
        fact[0] = 1;
        //dp[0] = 0;
        for(int i=1;i<=14;i++){
            fact[i]  = fact[i-1]*26;
            //dp[i] = dp[i-1]+fact[i];
            //System.out.println("i:"+i+" "+dp[i]);
        }
        n--;
        long k = n;
        int cnt = 1;
        while(k>=0){
            if(k>=fact[cnt]){
                k-=fact[cnt];
                cnt++;
            }else{
                break;
            }
        }
        //System.out.println(k+" "+cnt);
        helper(fact,cnt,k);

    }
    void helper(long[] fact, int len, long n){
        StringBuilder sb = new StringBuilder();
        for(int i=len;i>=1;i--){
            int idx = (int)n/(int)fact[i-1];
            n -= idx*fact[i-1];
            sb.append((char) (idx+'a'));
        }
        System.out.println(sb);

    }


    public static void main(String[] args)  throws IOException {
        // Use the Scanner class

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String[]  s = br.readLine().split(" ");
        Main test = new Main();

        long n = Long.parseLong(s[0]);

        test.solve(n);
        //int tot = Integer.parseInt(br.readLine());


//        int i =1;
//        System.out.println();
//        while(tot>0){
//
//            String s = br.readLine();
//            String[] sr = s.split(" ");
//            List<Long> ls = new ArrayList<>();
//            for(String ss:sr){
//                ls.add(Long.parseLong(ss));
//            }
//            Main tt = new Main();
//            tt.sol(ls);
//            // String Buffer to store answer
//            StringBuffer sb = new StringBuffer();
////            Solution obj = new Solution();
////
////            System.out.println("Case #"+i+": "+obj.sol());
//            tot--;
//            i++;
//        }
    }

}