#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> P;
int INF = 3e18+7;
int mod = 1e9+7;
int dx[] = {1, 0,-1, 0, 1, 1,-1,-1};
int dy[] = {0, 1, 0,-1, 1,-1, 1,-1};
signed main() {
    int N,M,P;
    cin >> N >> M >> P;
    vector<int>A(N);
    int mx = 1,mx2 = 1,mx3 = 1,mx4 = 0;
    bool flag = true;
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        mx = max(mx,A[i]);
        if(A[i]%P) {
            mx2 = max(mx,A[i]);
        }
        else {
            int tmp = A[i];
            while (tmp%P == 0) {
                tmp /= P;
            }
            if(tmp > 1) {
                flag = false;
            }
        }
    }
    for(int i = 0; i < N; i++) {
        if(A[i]%P == 0) {
            int tmp = A[i];
            int tmp2 = mx2;
            while (tmp%P == 0) {
                tmp /= P;
                tmp2 *= mx;
                if(tmp2 > M) {
                    tmp2 = M;
                }
            }
            if(tmp > 1) {
                flag = false;
            }
            if(tmp2 < tmp) {
                if(mx4 < tmp) {
                    mx3 = A[i];
                    mx4 = tmp;
                }
            }
        }
    }
    int X = 1;
    int ans = 0;
    if(X <= M && mx2 == 1 && X*mx <= M) {
        if(flag) {
            cout << -1 << endl;
            return 0;
        }
    }
    while (true) {
        if(X > M) {
            break;
        }
        if(X%M == 0) {
            X/=M;
        }
        else if(X*mx > M) {
            X*=mx;
        }
        else if(mx3 != 1) {
            X*=mx3;
        }
        else {
            X*=mx2;
        }
        ans++;
    }
    cout << ans << endl;
}