#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------


int N,M,A,B;
int C[5050];
int NG[5050];

ll dp[5050];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M>>A>>B;
	vector<int> V;
	for(i=1;i*i<=N;i++) if(N%i==0) {
		V.push_back(i);
		if(i*i!=N) V.push_back(N/i);
	}
	sort(ALL(V));
	
	
	FOR(i,M) cin>>NG[i];
	
	FOR(i,V.size()) dp[i]=1LL<<60;
	dp[0]=0;
	FOR(i,V.size()) {
		int mi=N+1;
		FOR(j,M) if(NG[j]%V[i]==0) mi=min(mi,NG[j]);
		for(j=i+1;j<V.size();j++) if(V[j]<mi&&V[j]%V[i]==0) {
			x=V[j]/V[i];
			dp[j]=min(dp[j],dp[i]+1LL*(x-1)*A+B);
		}
	}
	
	if(dp[V.size()-1]>=1LL<<60) {
		cout<<-1<<endl;
	}
	else {
		cout<<dp[V.size()-1]-B<<endl;
	}
	
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}