9 13
6 14 19 5 -5 6 -10 20 8
 8 9
6 -1 5 -5 -8 -7 -8 -7
 10 7
-9 3 -4 -22 4 -17 0 -14 3 -2
 6 2
-2 3 0 -2 0 0
 5 10
-8 -24 0 -22 12
 5 13756
-2 -9 -10 0 10
 7 3
1 -3 0 3 -1 0 2
 9 9
-3 2 0 -2 -7 -1 0 5 3
 2 3
2 0
 19 78701
1 0 -1 0 -1 -1 0 1 0 -1 1 1 -1 1 0 0 -1 0 0
 5 4
-1 0 0 1 -1
 6 4
-1 0 2 -4 0 5
 20 23036
-1 1 -1 -1 -1 -1 1 -1 -1 0 0 1 1 0 0 1 0 0 -1 -1
 5 4
-1 0 -3 0 3
 12 82016
1 -2 -1 -1 -2 -1 0 -2 -1 1 -2 2
 7 4
-6 0 2 -3 0 4 0
 4 4
2 2 0 1
 6 1
-3 0 0 0 -2 3
 8 26
-4 9 -14 -11 0 7 23 -15
 20 23079
0 1 1 -1 1 0 -1 -1 0 0 1 -1 1 1 1 0 0 1 0 1
 1 1
1
 7 8555
-2 -3 -2 3 0 -2 0
 4 100
-100 0 -50 100
 3 14
12 12 -8
 1 1
2
 10 23
9 7 14 16 -13 -22 24 -3 -12 14
 8 11
12 -12 -9 3 -22 -21 1 3
 19 49926
-2 0 2 0 0 -2 2 -1 -1 0 0 0 1 0 1 1 -2 2 2
 16 76798
-1 11 -7 -4 0 -11 -12 3 0 -7 6 -4 8 6 5 -10
 9 5
-2 0 3 -4 0 4 -3 -2 0

-1
 -1
 1
 1
 1
 1
 -1
 2
 0
 1
 1
 -1
 1
 1
 1
 1
 -1
 1
 -1
 0
 0
 1
 1
 -1
 -1
 -1
 -1
 1
 1
 1

#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n, m;
  cin >> n >> m;
  long long a[n + 1];
  long long pre[n + 1];
  pre[0] = 0;
  for (long long i = 1; i <= n; i++) {
    cin >> a[i];
    pre[i] = pre[i - 1] + a[i];
  }
  long long max_in_pre_i_to_n[n + 1];
  max_in_pre_i_to_n[n] = pre[n];
  for (long long i = n - 1; i >= 1; i--) {
    max_in_pre_i_to_n[i] = max(pre[i], max_in_pre_i_to_n[i + 1]);
  }
  long long sum_till_here = 0;
  long long extra_deposit = 0;
  long long times = 0;
  for (long long i = 1; i <= n; i++) {
    sum_till_here = pre[i] + extra_deposit;
    if (sum_till_here > m) {
      cout << "-1\n";
      return 0;
    }
    if (a[i] == 0) {
      if (sum_till_here < 0) {
        long long max_value = max_in_pre_i_to_n[i];
        long long how_much_i_have_to_deposit = -1 * sum_till_here;
        if (how_much_i_have_to_deposit + max_value > m) {
          cout << -1 << "\n";
          return 0;
        }
        extra_deposit += min(m - max_value, how_much_i_have_to_deposit + m);
        times++;
      }
    }
  }
  cout << times << "\n";
}
