import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    static HashMap<Integer, Integer> unables = new HashMap<>();
    static HashMap<Integer, Long> dp = new HashMap<>();
    static long a;
    static long b;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        a = sc.nextInt();
        b = sc.nextInt();
        int[] values = new int[m];
        for (int i = 0; i < m; i++) {
            values[i] = sc.nextInt();
        }
        Arrays.sort(values);
        for (int i = 1; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                unables.put(i, Integer.MAX_VALUE);
                if (i != 1 && i * i < n) {
                    unables.put(n / i, Integer.MAX_VALUE);
                }
            }
        }
        for (int x : unables.keySet()) {
            for (int y : values) {
                if (y % x == 0) {
                    unables.put(x, y);
                    break;
                }
            }
        }
        dp.put(1, 0L);
        long ans = dfw(n);
        if (ans >= Long.MAX_VALUE / 2) {
            System.out.println(-1);
        } else {
            System.out.println(ans - b);
        }
    }
    
    static long dfw(int x) {
        if (!dp.containsKey(x)) {
            long ans = Long.MAX_VALUE / 2;
            for (int y : unables.keySet()) {
                if (x == y || x % y > 0) {
                    continue;
                }
                if (unables.get(y) <= x) {
                    continue;
                }
                ans = Math.min(ans, dfw(y) + (x / y - 1) * a + b);
            }
            dp.put(x, ans);
        }
        return dp.get(x);
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}