#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<bitset>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#include<list>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<functional>
#include<cstdio>
#include<cstdlib>
#include<numeric>
using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define INF 2e9
//#define MOD 1000000007
#define MOD 998244353
#define LINF (long long)4e18
#define jck 3.141592

const double EPS = 1e-10;

using ll = long long;
using Pi = pair<int,int>;
using Pl = pair<ll,ll>;

int main(){
    int n,m,p; cin >> n >> m >> p;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    ll M = 0,M_p = 0;
    rep(i,n){
        if(a[i]%p == 0) M_p = max(M_p,a[i]);
        else M = max(M,a[i]);
    }
    ll k = M_p;
    while(k%p == 0) k /= p;
    if((M == 0||M == 1) and k == 1){
        cout << -1 <<endl;
        return 0;
    }
    ll x = 1;
    ll ans = 0;
    while(x < m) {
        if(x*M > m || x*M_p > m){
            ans++;
            break;
        }
        int cnt = 0;
        ll k = M_p;
        while(k%p == 0){
            k /= p;
            cnt++;
        }
        if(M ==1){
            ans += cnt+1;
            x *= k;
        }
        else {
            int cnt2 = 0;
            ll k2 = M;
            while(k2 < m){
                k2 *= M;
                cnt2++;
            }
            if(cnt2 < cnt){
                ans++;
                x *= M;
            }
            else{
                if(pow(M,cnt2) < k){
                    ans += cnt+1;
                    x *= k;
                }
                else{
                    ans++;
                    x *= M;
                }
            }
        }

    }
    cout << ans << endl;

}