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 Kotlin (1.3.71) (judge verdict: Accepted)

fun main() {
    val n = readLn().toLong()
    val pows26 = mutableListOf(26L)
    var p26 = 26L
    for (i in 1 until 11) {
        val last = pows26.last()
        pows26.add(last + p26 * 26)
        p26 *= 26
    }

    fun findNumberOfCharacters(): Int {
        for (i in pows26.indices) {
            if (n > pows26[i] && n <= pows26[i + 1]) return i + 2
        }

        return 1
    }

    val numOfChars = findNumberOfCharacters()

    var rep = n - 1
    if (numOfChars != 1) rep = n - pows26[numOfChars - 2] - 1

    val ans = mutableListOf<Char>()
    while (rep > 0) {
        ans.add(('a' + (rep % 26).toInt()))
        rep /= 26
    }

    while(ans.size < numOfChars) ans.add('a')

    println(ans.reversed().joinToString(""))
}

// Input Reader
private fun readLn() = readLine()!!