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>
class raw_input {
 public:
  template <typename T>
  raw_input& operator>>(T& arg) {
    if constexpr (std::is_integral<T>::value) {
      if constexpr (sizeof(T) == sizeof(int)) {
        scanf("%d", &arg);
      } else {
        scanf("%lld", &arg);
      }
    }
    if constexpr (std::is_floating_point<T>::value) {
      if constexpr (sizeof(T) == sizeof(double)) {
        scanf("%lf", &arg);
      } else {
        scanf("%LF", &arg);
      }
    }
    return *this;
  }
  raw_input& operator>>(char* arg) {
    scanf("%s", arg);
    return *this;
  }
  raw_input& operator>>(char& c) {
    while ((c = getchar()) != EOF && (c == ' ' || c == '\n'))
      ;
    return *this;
  }
} gin{};
using namespace std;
struct engine {
  bool used = false;
  int l, r;
  int mmim;
  int mumm;
  engine() {}
  void set(int l_, int r_) {
    l = l_;
    r = r_;
    mumm = 0;
    mmim = 0;
    used = true;
  }
  void update(int hmm) { mmim = max(mmim, hmm); }
  int get() { return l; }
  int how() {
    int mine = max(0, r - (mmim + mumm));
    return min(r - l, mine);
  }
  void increment(int v) {
    mumm += v;
    l += v;
  }
} e{};
int a[100005];
int main() {
  int n, d;
  gin >> n >> d;
  for (int i = (0); i <= (n - 1); ++i) gin >> a[i];
  long long prev = 0;
  int ans = 0;
  for (int i = (0); i <= (n - 1); ++i) {
    prev += a[i];
    if (e.used && e.get() + prev > d) {
      cout << -1 << endl;
      return 0;
    }
    if (e.used == false && prev > d) {
      cout << -1 << endl;
      return 0;
    }
    if (a[i] == 0 && prev < 0) {
      if (e.used) {
        int inc = e.how();
        if (inc + prev >= 0) {
          int mmim = min(abs(prev), 1LL * inc);
          e.increment(mmim);
          prev += mmim;
        } else {
          ++ans;
          e.set(0, d);
          prev = 0;
        }
      } else {
        e.set(0, d);
        prev = 0;
        ++ans;
      }
    }
    e.update(prev);
  }
  cout << ans << endl;
  return 0;
}
