#include<bits/stdc++.h>
#define int long long
using namespace std;
const int INF=1e18;
signed main(){
    int N,M,P,mx=0;cin>>N>>M>>P;
    vector<int> A(N);
    for(int i=0;i<N;i++){
        cin>>A[i];
        mx=max(mx,A[i]);
    }
    int ans=INF,m=M/mx+1;
    for(int i=0;i<N;i++){
        int a=1,b=1,cnt=1;
        while(A[i]%P==0)A[i]/=P,a++;
        if(A[i]==1){
            if(m==1)ans=1;
            continue;
        }
        while(b<m)b*=A[i],cnt+=a;
        ans=min(ans,cnt);
    }
    cout<<(ans==INF?-1:ans)<<endl;
}