#include <stdio.h>

const long long sup = 1LL << 60;

typedef struct Edge {
	struct Edge *next;
	int v;
	long long cost;
} edge;

void chmin(int* a, int b)
{
	if (*a > b) *a = b;
}

int main()
{
	int i, N, M, A, B, C[5001];
	scanf("%d %d %d %d", &N, &M, &A, &B);
	for (i = 1; i <= M; i++) scanf("%d", &(C[i]));
	
	int n = 0, div[2001];
	for (i = 1; i * i <= N; i++) {
		if (N % i != 0) continue;
		div[++n] = i;
		if (i * i != N) div[++n] = N / i;
	}
	
	int m = 0, u, w, min;
	edge *adj[2001] = {}, e[2000001], *p;
	for (u = 1; u <= n; u++) {
		for (i = 1, min = N + 1; i <= M; i++) if (C[i] % div[u] == 0) chmin(&min, C[i]);
		for (w = 1; w <= n; w++) {
			if (w == u || div[w] % div[u] != 0 || min <= div[w]) continue;
			e[m].v = w;
			e[m].cost = (long long)A * (div[w] / div[u] - 1) + B;
			e[m].next = adj[u];
			adj[u] = &(e[m++]);
		}
	}
	
	int flag[2001] = {}, argmin;
	long long dist[2001], minll;
	for (u = 2, dist[1] = -B; u <= n; u++) dist[u] = sup;
	while (1) {
		for (u = 1, minll = sup; u <= n; u++) {
			if (flag[u] == 0 && minll > dist[u]) {
				minll = dist[u];
				argmin = u;
			}
		}
		if (minll == sup) break;
		u = argmin;
		flag[u] = 1;
		for (p = adj[u]; p != NULL; p = p->next) {
			w = p->v;
			if (dist[w] > dist[u] + p->cost) dist[w] = dist[u] + p->cost;
		}
	}
	if (dist[2] == sup) printf("-1\n");
	else printf("%lld\n", dist[2]);
	fflush(stdout);
	return 0;
}