#include <bits/stdc++.h>

using i32 = int32_t;
using ui32 = uint32_t;
using i64 = int64_t;
using ui64 = uint64_t;

using namespace std;


i32 main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int x, n;
  cin >> x >> n;
  vector<int> arr(n);
  for (int i = 0; i < n; i++) cin >> arr[i];
  int ans = 0;
  while (arr.size()) {
    while (arr.size() && arr.back() == 0) arr.pop_back();
    if (arr.size()) {
      int cur = x;
      while (cur-- && arr.size()) arr.pop_back();
      ans++;
    }
  }
  cout << ans << endl;
}