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()!!