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>
template <class T>
class segment_tree_t {
 public:
  segment_tree_t(int size)
      : max_(NULL), add_(NULL), xm_(std::numeric_limits<T>::min()) {
    resize(size);
  };
  segment_tree_t() { segment_tree_t(0); };
  ~segment_tree_t() {
    delete[] max_;
    delete[] add_;
  };

 public:
  void resize(int size) {
    delete[] max_;
    delete[] add_;
    for (size_ = 1; size_ < size; size_ <<= 1)
      ;
    max_ = new T[size_ * 2];
    add_ = new T[size_ * 2];
    memset(max_, 0, sizeof(T) * size_ * 2);
    memset(add_, 0, sizeof(T) * size_ * 2);
  };

 public:
  void add(int a, int b, T x, int k = -1, int l = -1, int r = -1) {
    if (k == -1) {
      add(a, b, x, 0, 0, size_);
    } else {
      assert(k < size_ * 2);
      if (r <= a || b <= l) return;
      if (a <= l && r <= b) {
        add_[k] += x;
      } else {
        add(a, b, x, k * 2 + 1, l, (l + r) / 2);
        add(a, b, x, k * 2 + 2, (l + r) / 2, r);
        max_[k] = std::max(max_[k * 2 + 1] + add_[k * 2 + 1],
                           max_[k * 2 + 2] + add_[k * 2 + 2]);
      }
    }
  };
  T query(int a, int b, int k = -1, int l = -1, int r = -1) const {
    if (k == -1) return query(a, b, 0, 0, size_);
    assert(k < size_ * 2);
    if (r <= a || b <= l) return xm_;
    if (a <= l && r <= b) return max_[k] + add_[k];
    long long xl = query(a, b, k * 2 + 1, l, (l + r) / 2);
    long long xr = query(a, b, k * 2 + 2, (l + r) / 2, r);
    return std::max(xl, xr) + add_[k];
  };

 private:
  int size_;
  T* max_;
  T* add_;
  T xm_;
};
int main(int argc, char** argv) {
  std::cin.tie(0);
  std::ios_base::sync_with_stdio(0);
  std::cout << std::fixed << std::setprecision(6);
  int n, d, a[111111], acc = 0;
  std::cin >> n >> d;
  segment_tree_t<long long> tree(n);
  for (int i = 0; i < n; i++) {
    std::cin >> a[i];
    acc += a[i];
    tree.add(i, i + 1, acc);
  }
  int c = 0;
  for (int i = 0; i < n; i++)
    if (a[i] == 0) {
      long long x = tree.query(i, i + 1);
      if (x > d) {
        c = -1;
        break;
      } else if (x >= 0) {
        ;
      } else {
        int dx = d - tree.query(i, n);
        if (dx <= 0) {
          c = -1;
          break;
        } else if (x + dx < 0) {
          c = -1;
          break;
        }
        tree.add(i, n, dx);
        c++;
      }
    }
  std::cout << c << std::endl;
  return 0;
}
