#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<ll,int>;
#define sr string 
#define vc vector
#define db double
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
	int n,m,a,b;cin>>n>>m>>a>>b;
	vc<int>ban(m); rep(i,m)cin>>ban[i];
	vc<int>d;
	for(int i=1;i*i<=n;i++)if(n%i==0){
		d.pb(i);
		if(i!=n/i)d.pb(n/i);
	}
	int k=d.size();
	sort(all(d));
	vc v(k,vc<int>(0));
	rep(i,k){
		int b=n+1;
		rep(j,m)if(ban[j]%d[i]==0)b=min(b,ban[j]);
		for(int j=i+1;j<k;j++)if(d[j]%d[i]==0){
			if(d[j]>=b)break;
			v[i].pb(j);
		}
	}
	pque<pp,vc<pp>,greater<pp>>q;
	vc<ll>dist(k,1e18);
	dist[0]=0; q.push({0,0});
	while(q.size()){
		auto [di,x]=q.top(); q.pop();
		if(dist[x]<di)continue;
		for(auto au:v[x]){
			ll cost=b+(ll)a*(d[au]/d[x]-1);
			if(dist[au]<=dist[x]+cost)continue;
			dist[au]=dist[x]+cost;
			q.push({dist[au],au});
		}
	}
	if(dist[k-1]==1e18)cout<<-1;
	else cout<<dist[k-1];
}