#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=1167167167167167167;
const int INF=2100000000;
const ll mod=1e9+7;
#define rep(i,a) for (int i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}



template<class T>
using square_matrix=std::vector<std::vector<T>>;
template<class T,T (*add_op)(T,T),T(*add_e)(),T (*mul_op)(T,T),T(*mul_e)()>
square_matrix<T> mul_matrix(square_matrix<T> l,square_matrix<T> r){
	int n=l.size();
	assert((int)l[0].size()==n&&(int)r.size()==n&&(int)r[0].size()==n);
	square_matrix<T> val(n,std::vector<T>(n,add_e()));
	for(int i=0;i<n;i++) for(int j=0;j<n;j++) for(int k=0;k<n;k++){
		val[i][k]=add_op(val[i][k],mul_op(l[i][j],r[j][k]));
	}
	return val;
}
template<class T,T (*add_op)(T,T),T(*add_e)(),T (*mul_op)(T,T),T(*mul_e)()>
square_matrix<T> pow_matrix(square_matrix<T> l,long long times){
	int n=l.size();
	square_matrix<T> val(n,std::vector<T>(n,add_e()));
	for(int i=0;i<n;i++) val[i][i]=mul_e();
	while(times){
		if(times&1){
			val=mul_matrix<T,add_op,add_e,mul_op,mul_e>(val,l);
		}
		l=mul_matrix<T,add_op,add_e,mul_op,mul_e>(l,l);
		times>>=1;
	}
	return val;
}

using mat_F=bool;
mat_F add_op(mat_F a,mat_F b){
	return a|b;
}
mat_F add_e(){
	return 0;
}
mat_F mul_op(mat_F a,mat_F b){
	return a&b;
}
mat_F mul_e(){
	return 1;
}
#define calc mat_F,add_op,add_e,mul_op,mul_e



void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	ll N,M,P;
	cin>>N>>M>>P;
	ll tmp;
	vector<ll> A(N),B(N),C(N,1);
	ll max_A=1;
	rep(i,N){
		cin>>tmp;
		A[i]=tmp;
		chmax(max_A,tmp);
		while(tmp%P==0) C[i]++,tmp/=P;
		B[i]=tmp;
	}
	ll X=(M+max_A)/max_A;
	ll ans=INF;
	rep(i,N){
		if(B[i]==1) continue;
		tmp=1;
		ll Y=0;
		while(tmp<X) tmp*=B[i],Y+=C[i];
		chmin(ans,Y+1);
	}
	if(ans==INF) cout<<"-1\n";
	else cout<<ans<<"\n";
}