
fun Long.toAlphabetBase(): String {
    val chars = ('a' .. 'z').toList()
    fun f(length: Int, value: Long): String {
        return when(length) {
            0 -> ""
            else -> f(length - 1, value / 26) + chars[(value % 26).toInt()]
        }
    }
    fun length(value: Int): Long {
        return when(value) {
            0 -> 1L
            else -> 26 * length(value - 1)
        }
    }
    var value = this - 1
    var len = 1
    while (length(len) <= value) {
        value -= length(len++)
    }
    return f(len, value)
}
fun main() {
    val n = readLine()!!.trim().toLong()
    println(n.toAlphabetBase())
}