#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;
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        mx = max(mx,A[i]);
        if(A[i]%P) {
            mx2 = max(mx,A[i]);
        }
    }
    int X = 1;
    int ans = 0;
    if(X <= M && mx2 == 1 && X*mx <= M) {
        cout << -1 << endl;
        return 0;
    }
    while (true) {
        if(X > M) {
            break;
        }
        if(X*mx > M) {
            X*=mx;
        }
        else {
            X*=mx2;
        }
        ans++;
    }
    cout << ans << endl;
}