import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val m = nextLong()
    val p = nextLong()
    val a = Array(n) { nextLong() }
    val b = a.copyOf()
    val c = Array(n) { 0 }
    for (i in 0 until n) {
        while (b[i] % p == 0L) {
            b[i] /= p
            c[i]++
        }
    }
    val max_a = a.max()!!
    val max_b = b.max()!!
    val cnt = (0 until n).filter { b[it] == max_b }.map { c[it] }.min()!!
    if (max_b == 1L && max_a < m) {
        println(-1)
        return
    }
    var now = 1L
    var ans = 0
    while (now <= m) {
        if (now * max_a > m) {
            ans++
            break
        } else {
            now *= max_b
            ans += cnt + 1
        }
    }
    println(ans)
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()!!
fun nextDouble() = next().toDouble()
// endregion