#line 2 "/home/defineprogram/Desktop/Library/template/template.cpp"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (int i = 0; i < n; i++)
#define REP(i, n) for (int i = 1; i < n; i++)
#define rev(i, n) for (int i = n - 1; i >= 0; i--)
#define all(v) v.begin(), v.end()
#define P pair<ll, ll>
#define len(s) (ll) s.size()

template <class T, class U>
inline bool chmin(T &a, U b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T, class U>
inline bool chmax(T &a, U b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
constexpr ll inf = 3e18;
#line 2 "main.cpp"

int N;
ll M,p;
ll A[1<<18];
int main() {
    cin.tie(0); ios::sync_with_stdio(false);
    cin>>N>>M>>p;
    ll mx=0;
    rep(i,N){
        cin>>A[i];
        chmax(mx,A[i]);
    }
    int ans=1e9;
    rep(i,N){
        int cnt=1;
        while(A[i]%p==0){
            A[i]/=p;cnt++;
        }
        if(A[i]!=1){
            int cc=0,now=1;
            while(now*mx<=M){
                now*=A[i];
                cc+=cnt;
            }
            chmin(ans,cc+1);
        }
    }
    if(ans==1e9)cout<<"-1\n";
    else cout<<ans<<"\n";
}