#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll n, m, p;
    cin >> n >> m >> p;
    ll a[n] = {};
    ll ma = 0;
    rep(i,n){
        cin >> a[i];
        ma = max(ma, a[i]);
    } 
    if(ma > m){
        cout << 1 << endl;
        return 0;
    }
    ll b[n] = {}, f[n] = {};
    ma = 0;
    rep(i,n){
        b[i] = a[i];
        while(b[i] % p == 0){
            f[i]++;
            b[i] /= p;
        }
        ma = max(ma, b[i]);
    }
    if(ma <= 1){
        cout << -1 << endl;
        return 0;
    }
    
    ll c[100] = {};
    rep(i,100) c[i] = 1;
    rep(i,n){
        c[f[i]] = max(c[f[i]], b[i]);
    }
    const ll INF = 1001001001;
    ll dp[2000];
    rep(i,2000) dp[i] = 1;
    rep(i,1000){
        rep(j,100){
            dp[i+j+1] = max(dp[i+j+1], dp[i] * c[j]);
            if(dp[i+j+1] > INF) dp[i+j+1] = INF;
        }
    }
    ma = 0;
    rep(i,n) ma = max(ma, a[i]);
    int ans = 1001001;
    rep(i,2000){
        if(dp[i] * ma > m){
            ans = min(ans, i+1);
        }
    }
    cout << ans << endl;
    return 0;
}