#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1E4 + 10;
bool st[MAXN];
int n, k, l, f[1 << 20], dis[25][25], id[MAXN], d[MAXN], tot;
vector<int> g[MAXN];
queue<int> q;
inline void add(int u, int v) {
  g[u].push_back(v);
  g[v].push_back(u);
}
void bfs(int s) {
  memset(d, 0x3f, sizeof d);
  d[s] = 0;
  q.push(s);
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    for (int v : g[x])
      if (d[v] == 0x3f3f3f3f) {
        d[v] = d[x] + 1;
        q.push(v);
      }
  }
  for (int i = 1; i <= n; i++)
    if (id[i]) dis[id[i]][id[s]] = min(dis[id[i]][id[s]], d[i]);
}
int main() {
  scanf("%d%d%d", &n, &k, &l);
  for (int i = 1, x; i <= k; i++) {
    scanf("%d", &x);
    st[x - 1] ^= 1;
    st[x] ^= 1;
  }
  for (int i = 0; i <= n; i++)
    if (st[i]) id[i] = ++tot;
  for (int i = 1, x; i <= l; i++) {
    scanf("%d", &x);
    for (int j = 1; j <= n - x + 1; j++) add(j - 1, j + x - 1);
  }
  memset(dis, 0x3f, sizeof dis);
  for (int i = 0; i <= n; i++)
    if (id[i]) bfs(i);
  memset(f, 0x3f, sizeof f);
  f[0] = 0;
  for (int s = 1; s < (1 << tot); s++)
    for (int i = 0; i < tot; i++)
      if ((s >> i) & 1)
        for (int j = 0; j < tot; j++)
          if ((s >> j) & 1)
            f[s] = min(f[s], f[s ^ (1 << i) ^ (1 << j)] + dis[i + 1][j + 1]);
  if (f[(1 << tot) - 1] == 0x3f3f3f3f)
    puts("-1");
  else
    printf("%d\n", f[(1 << tot) - 1]);
}
