#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int N,M,A,B;
int C[5000];
int main()
{
	cin>>N>>M>>A>>B;
	for(int i=0;i<M;i++)cin>>C[i];
	sort(C,C+M);
	vector<int>dv;
	for(int i=1;i*i<=N;i++)if(N%i==0)
	{
		dv.push_back(i);
		if(i<N/i)dv.push_back(N/i);
	}
	sort(dv.begin(),dv.end());
	vector<long long>dp(dv.size(),(long long)1e18);
	dp[0]=0;
	vector<int>tmp;
	for(int i=0;i<dv.size();i++)
	{
		tmp.clear();
		for(int j=0;j<M;j++)if(C[j]%dv[i]==0)tmp.push_back(C[j]);
		for(int j=i+1;j<dv.size();j++)if(dv[j]%dv[i]==0)
		{
			if(lower_bound(tmp.begin(),tmp.end(),dv[i])==upper_bound(tmp.begin(),tmp.end(),dv[j]))
			{
				dp[j]=min(dp[j],dp[i]+B+dv[j]/dv[i]*(long long)A-A);
			}
		}
	}
	if(dp[dv.size()-1]==(long long)1e18)cout<<-1<<endl;
	else cout<<dp[dv.size()-1]-B<<endl;
}