#include <bits/stdc++.h>
using namespace std;
int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int n;
  long long m,p;
  cin>>n>>m>>p;
  long long tmp;
  long long min_a=-1;
  for(int i=0;i<n;i++){
    cin>>tmp;
    if (tmp>m){
      min_a=1;
    }else{
      long long cnt=0;
      while(tmp%p==0){
	cnt++;
	tmp/=p;
      }
      if (tmp==1) continue;
      if(min_a==-1){
	min_a=ceil(log(m)/log(tmp))+cnt*(ceil(log(m)/log(tmp))-1);
      }else{
	min_a=min(min_a,(long long)ceil(log(m)/log(tmp))+cnt*((long long)ceil(log(m)/log(tmp))-1));
      }
    }
    
  }
  cout<<min_a<<"\n";
  return 0;
}