#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

ll p;

pair<double,ll> f(ll x){
  ll y=x;
  ll c=1;
  while(x%p==0){
    x/=p;
    c++;
  }
  if(x==1) return {0,-1};
  else if(c==1) return {y,1};
  else return {pow((double)y,1/(double)c),c};
}

int main(){
  ll n,m;
  cin>>n>>m>>p;
  
  vector<ll> A(n);
  rep(i,n) cin>>A[i];
  
  ll ma=0;
  rep(i,n) ma=max(ma,A[i]);
  
  if(ma>m){
    cout<<1<<endl;
    return 0;
  }
  
  ll g=(m+ma-1)/ma;
  
  vector<pair<double,ll>> B(n);
  rep(i,n) B[i]=f(A[i]);
  
  double ma1=0;
  ll d;
  rep(i,n){
    if(ma1<B[i].first){
      ma1=B[i].first;
      d=B[i].second;
    }
    else if(ma1==B[i].first && d>B[i].second){
      d=B[i].second;
    }
  }
  
  if(ma1<1.0000000001){
    cout<<-1<<endl;
    return 0;
  }
  
  double now=1;
  int cnt=0;
  while(now<=g+0.00000000001){
    now*=ma1;
    cnt+=d;
  }
  cout<<cnt+1<<endl;

  return 0;
}