#include<bits/stdc++.h>
using ll=long long;
using std::cin;
using std::cout;
using std::endl;
using std::vector;
int main(){
    ll N,M,P; cin>>N>>M>>P;
    vector<ll> max(31,1);
    vector<ll> dp(601);
    dp[0]=1;
    ll biggest=0;
    while(N--){
        ll X; cin>>X;
        biggest=std::max(biggest,X);
        ll cnt=0;
        while(X%P==0){
            X/=P;
            cnt++;
        }
        max[cnt]=std::max(max[cnt],X);
    }
    for(int i=0;i<600;i++){
        if(dp[i]*biggest>M){
            cout<<i+1<<endl;
            return 0;
        }
        for(int j=0;j<=30;j++){
            if(i+j+1>600) break;
            dp[i+j+1]=std::max(dp[i+j+1],dp[i]*max[j]);
        }
    }
    cout<<-1<<endl;
}