fun main() {
    val builder = StringBuilder()

    val n = readInputLine().toLong()

    var nTmp = n

    var len = 0

    var currentBase = 26L
    var currentSum = 0L

    while (true) {
        len++
        currentSum += currentBase

        if (currentSum >= n) {
            break
        }

        nTmp -= currentBase

        currentBase *= 26L
    }

    val ans = CharArray(len) { 'a' }

    val str = (nTmp - 1L).toString(26).padStart(len, '0')

    for (i in str.indices) {
        ans[i] = 'a' + str[i].toString().toInt(26)
    }

    builder.appendln(ans.joinToString(""))

    print(builder.toString())
}

fun readInputLine(): String {
    return readLine()!!
}
