#include <iostream>
#include <map>
#include <set>
#include <algorithm>
#include <vector>

using namespace std;
typedef long long ll;
ll c[5010];
int main(){
    ll i,n,m,a,b; cin >> n >> m >> a >> b;
    for(i=0;i<m;i++) cin >> c[i];
    sort(c,c + m);
    map<ll,ll> mp;
    set<ll> s;
    mp[1] = 0; s.insert(1);
    while(s.size()){
        ll x = *s.begin(); s.erase(x);
        ll nn = n/x;
        ll val = mp[x];
        vector<ll> d1,d2;
        for(i=1;i*i<=nn;i++){
            if(nn%i==0){
                if(i!=1) d1.push_back(i);
                if(i*i!=nn) d2.push_back(nn/i);
            }
        }
        reverse(d2.begin(),d2.end());
        d1.insert(d1.end(),d2.begin(),d2.end());
        int j = 0;
        for(i=0;i<d1.size();i++){
            int now = d1[i]*x;
            bool f = false;
            while(j<m && c[j]<=now){
                if(c[j]>=x && c[j]%x==0) f = true;
                j++;
            }
            if(f) break;
            s.insert(now);
            //if(now==6) cout << d1[i] << " vvv " << val << " " << x << endl;
            if(mp.find(now)==mp.end()) mp[now] = val + (ll)(d1[i] - 1)*a + b;
            else mp[now] = min(mp[now],val + (ll)(d1[i] - 1)*a + b);
        }
    }
    if(mp.find(n)==mp.end()) cout << -1 << "\n";
    else cout << mp[n] - b << "\n";
    //for(auto x:mp) cout << x.first << " " << x.second << "\n";
}