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 Scala (2.13.1) (judge verdict: Accepted)

import java.util.Scanner

object Main extends App {

  def readALine(c:Int, ac:List[Int]=Nil):List[Int] =
    if (c > 0) readALine(c-1, sc.nextInt::ac) else ac.reverse
  // def readLines(r:Int, c:Int, ac:List[List[Int]]):List[List[Int]] =
  //   if (r > 0) readLines(r-1, c, readALine(c, Nil)::ac) else ac.reverse
  val sc = new Scanner(System.in)
  val N = sc.nextLong

  def power(base:Int, exp:Int):Long = {
    def iter(f:Long, e:Int, ac:Long):Long = {
      if (e==0) ac else {
        val e_ = e >> 1
        val f_ = f*f
        if ((e & 1) > 0) iter(f_, e_, ac*f) else iter(f_, e_, ac)
      }
    }
    iter(base, exp, 1)
  }

  val divisor = 26

  def solver(n:Long, al:List[Int]):List[Int] = {
    // println(s"debug n:$n al:$al")
    if (n < divisor && n / divisor ==0)
      (n % divisor).toInt::al
    else
      solver((n-divisor)/divisor, ((n-divisor) % divisor).toInt::al)
  }

  println(solver(N-1, Nil).map((x)=>(x+97).toChar).mkString(""))

}