//GIVE ME AC!!!!!!!!!!!!!!!!!
#include<bits/stdc++.h>
#define ll long long
#define MOD 1000000007
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
int main(){
   int n,m,p;
   cin>>n>>m>>p;
    vector<pair<int,int>>a(n);
    int one=0;
    rep(i,n){
        int b;
        cin>>b;
        int sum=0;
        while(b%p==0){
            b/=p;
           sum++;
        }
        if(b==1){
            one++;
        }
        a[i]=make_pair(b,sum);
    }
    sort(a.begin(),a.end());
    int ans=0;
    int start=1;
    if(one==n){
        cout<<-1<<endl;
    }
    else{
        while(start<=m){
           int aa=a[n-1].second;
            ans+=1+aa;
            start*=a[n-1].first;
        }
       cout<<ans<<endl;
    }
}