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;
class SegTree_Max {
  vector<int> st, st2, id;
  vector<int> lazy;
  int n;
  void prop(int p, int L, int R) {
    if (lazy[p]) {
      st[p] += lazy[p];
      lazy[2 * p] += lazy[p];
      lazy[2 * p + 1] += lazy[p];
      lazy[p] = 0;
    }
  }
  void upd(int p, int L, int R, int i, int j, int v) {
    prop(p, L, R);
    if (j < L || i > R) {
      return;
    }
    if (i <= L && R <= j) {
      lazy[p] = v;
      prop(p, L, R);
      return;
    }
    int mid = (L + R) / 2;
    upd(2 * p, L, mid, i, j, v);
    upd(2 * p + 1, mid + 1, R, i, j, v);
    st[p] = max(st[2 * p], st[2 * p + 1]);
  }
  int qry(int p, int L, int R, int i, int j) {
    prop(p, L, R);
    if (j < L || i > R) {
      return -1e9;
    }
    if (i <= L && R <= j) {
      return st[p];
    }
    int mid = (L + R) / 2;
    return max(qry(2 * p, L, mid, i, j), qry(2 * p + 1, mid + 1, R, i, j));
  }

 public:
  SegTree_Max(int sz) {
    n = sz;
    st.assign(9 * (n + 1), 0);
    lazy.assign(9 * (n + 1), 0);
  }
  int qry(int i, int j) { return qry(1, 1, n, i, j); }
  void upd(int i, int j, int v) { upd(1, 1, n, i, j, v); }
};
class SegTree_Sum {
  vector<int> st, st2, id;
  vector<int> lazy;
  int n;
  void prop(int p, int L, int R) {
    if (lazy[p]) {
      st[p] += lazy[p];
      lazy[2 * p] += lazy[p];
      lazy[2 * p + 1] += lazy[p];
      lazy[p] = 0;
    }
  }
  void upd(int p, int L, int R, int i, int j, int v) {
    prop(p, L, R);
    if (j < L || i > R) return;
    if (i <= L && R <= j) {
      lazy[p] = v;
      prop(p, L, R);
      return;
    }
    int mid = (L + R) / 2;
    upd(2 * p, L, mid, i, j, v);
    upd(2 * p + 1, mid + 1, R, i, j, v);
    int qryLo = st[2 * p];
    int qryHi = st[2 * p + 1];
    st[p] = qryLo + qryHi;
  }
  int qry(int p, int L, int R, int i, int j) {
    prop(p, L, R);
    if (j < L || i > R) return 0;
    if (i <= L && R <= j) return st[p];
    int mid = (L + R) / 2;
    int qryLo = qry(2 * p, L, mid, i, j);
    int qryHi = qry(2 * p + 1, mid + 1, R, i, j);
    return qryLo + qryHi;
  }

 public:
  SegTree_Sum(int sz) {
    n = sz;
    st.assign(9 * (n + 1), 0);
    lazy.assign(9 * (n + 1), 0);
  }
  int qry(int i, int j) { return qry(1, 1, n, i, j); }
  void upd(int i, int j, int v) { upd(1, 1, n, i, j, v); }
};
int main() {
  ios::sync_with_stdio(false);
  int n, d, x, tot = 0;
  cin >> n >> d;
  SegTree_Sum st_sum(n);
  SegTree_Max st_max(n);
  vector<int> v(n + 1);
  for (int(i) = (1), _MAX = (n + 1); (i) < _MAX; (i)++) {
    cin >> x;
    v[i] = x;
    st_sum.upd(i, i, x);
    st_max.upd(i, i, st_sum.qry(1, i));
    if (st_sum.qry(1, i) > d) {
      cout << -1 << endl;
      return 0;
    }
  }
  for (int(i) = (1), _MAX = (n + 1); (i) < _MAX; (i)++) {
    int val = st_sum.qry(1, i);
    if (v[i] == 0 && val < 0) {
      int mx = st_max.qry(i, n);
      mx = d - mx;
      if (val + mx < 0) {
        cout << -1 << endl;
        return 0;
      }
      st_sum.upd(i, i, mx);
      st_max.upd(i, n, mx);
      tot++;
    }
  }
  cout << tot << endl;
  return 0;
}
