import java.util.Scanner

fun main() {
	val scn = Scanner(System.`in`)
	var n = scn.nextLong()
	var s = ""
	var d = 1
	var dk = 26L
	val pw = mutableListOf(26L)
	while (n>dk){
		pw.add(pw.last()*26)
		dk += pw.last()
		d++
	}
	n -= dk-pw.last() + 1
	val a = 'a'.toInt()
	repeat(d){
		val r = (n%26).toInt()
		s = (a+r).toChar() + s
		n /= 26
	}
	println(s)
}