#include <bits/stdc++.h>
using namespace std;
#define REP(i, n) FOR(i, 0, (n))
#define FOR(i, a, b) for(int i=(a); i<(b); i++)
#define LAR(a, b) ((a)=max((a),(b)))
#define SML(a, b) ((a)=min((a),(b)))
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vl = vector<ll>;
using pii = pair<int, int>;
using vpii = vector<pair<int, int>>;
template<typename T>
using pque = priority_queue<T, vector<T>, greater<T>>;
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define ALL(a) (a).begin(), (a).end()
#ifdef LOCAL_DEBUG
#define DEBUG(...) printf(__VA_ARGS__)
#else
#define DEBUG(...)
#endif

ll a[212345];
ll b[212345];

int main(){
	int n; ll m, p; scanf("%d%lld%lld", &n, &m, &p);
	REP(i, n) scanf("%lld", a+i);
	REP(i, n){
		b[i] = a[i];
		while(b[i] % p == 0) b[i] /= a[i];
	}
	ll *y = max_element(a, a+n);
	ll *z = max_element(b, b+n);
	int ans = 0;
	ll x = 1;
	while(x <= m){
		if(x * *y > m) {
			ans++;
			break;
		}
		if(*z == 1) {
			ans = -1;
			break;
		}
		x *= *(z-b+a);
		ans++;
		while(x % p == 0){
			x /= p;
			ans++;
		}
	}
	printf("%d\n", ans);
}