#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000


int main() {
	
	long long N,M,A,B;
	cin>>N>>M>>A>>B;
	
	vector<long long> c(M);
	rep(i,M)cin>>c[i];
	
	vector<long long> y;
	for(long long i=1;i*i<=N;i++){
		if(N%i==0){
			y.push_back(i);
			if(i*i!=N){
				y.push_back(N/i);
			}
		}
	}
	
	sort(y.begin(),y.end());
	
	vector<long long> dp(y.size(),Inf);
	dp[0] = 0;
	
	rep(i,y.size()){
		if(dp[i]==Inf)continue;
		long long ng = Inf;
		rep(j,M){
			if(c[j]%y[i]==0 && c[j]>=y[i])ng = min(ng,c[j]);
		}
		//cout<<y[i]<<','<<ng<<endl;
		for(int j=i+1;j<y.size();j++){
			if(y[j] >= ng)break;
			if(y[j] % y[i] != 0)continue;
			long long nv = dp[i];
			nv += (y[j] / y[i] - 1) * A + B;
			dp[j] = min(dp[j],nv);
		}
	}
	
	long long ans = dp.back();
	if(ans==Inf)ans = -1;
	else ans -= B;
	
	cout<<ans<<endl;
		
	
    return 0;
}