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;
using lli = long long int;
template <class T>
class segtree {
 public:
  lli n;
  vector<T> dat;
  function<T(T, T)> func;
  T dummy;
  segtree<T>(lli _n, T ini, function<T(T, T)> f, T dummy)
      : func(f), dummy(dummy) {
    n = 1;
    while (n < _n) {
      n = n * 2;
    }
    dat.assign(2 * n - 1, ini);
  }
  void update(lli k, T a) {
    k += n - 1;
    dat[k] = a;
    while (k > 0) {
      k = (k - 1) / 2;
      dat[k] = func(dat[k * 2 + 1], dat[k * 2 + 2]);
    }
  }
  T query(int a, int b) { return query(a, b, 0, 0, n); }
  T query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l) return dummy;
    if (a <= l && r <= b)
      return dat[k];
    else {
      T vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
      T vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
      return func(vl, vr);
    }
  }
  T get(int a) { return query(a, a + 1, 0, 0, n); }
};
int main() {
  using p = lli;
  auto f = [](p a, p b) -> p { return max(a, b); };
  lli first = 0;
  lli n, d;
  cin >> n >> d;
  segtree<p> seg(n + 10, first, f, first);
  lli cur = 0;
  int ans = 0;
  lli use = 0;
  lli a[100005] = {};
  vector<int> v;
  for (lli i = 0; i < (n); i++) {
    cin >> a[i];
    if (a[i] == 0) {
      v.push_back(i);
    }
  }
  lli memo[100005] = {};
  lli sum = 0;
  lli ch = 0;
  for (lli i = 0; i < (n); i++) {
    sum += a[i];
    ch += a[i];
    if (a[i] == 0) ch = 0;
    if (ch > d) {
      cout << -1 << endl;
      return 0;
    }
    memo[i + 1] = sum;
    seg.update(i + 1, sum);
  }
  for (lli i = 0; i < (n); i++) {
    if (a[i] == 0) {
      if (cur < 0) {
        cur = d - (seg.query(i + 1, n + 1) - memo[i]);
        use++;
      }
    } else {
      cur += a[i];
      if (cur > d) {
        cout << -1 << endl;
        return 0;
      }
    }
  }
  cout << use << endl;
}
