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;
const long long infll = powl(2, 62) - 1;
const long double pi = 4.0 * atanl(1.0);
const long long mod = powl(10, 9) + 7;
struct SegmentTree {
 private:
  long long function(long long a, long long b) { return max(a, b); }
  vector<long long> tree, lazy;
  long long n, root, size;

 public:
  SegmentTree(vector<long long> &arr) : n(arr.size()), root(1) {
    long long x = (long long)(ceil(log2(n)));
    size = 2 * (long long)pow(2, x);
    tree.resize(size);
    lazy.resize(size);
    build(arr, root, 0, n - 1);
  }
  void build(vector<long long> &arr, long long node, long long start,
             long long end) {
    if (start == end)
      tree[node] = arr[start];
    else {
      long long mid = (start + end) / 2;
      build(arr, 2 * node, start, mid);
      build(arr, 2 * node + 1, mid + 1, end);
      tree[node] = function(tree[2 * node], tree[2 * node + 1]);
    }
  }
  void pendingUpdate(long long node, long long start, long long end) {
    if (lazy[node]) {
      tree[node] += (end - start + 1) * lazy[node];
      if (start != end) {
        lazy[2 * node] += lazy[node];
        lazy[2 * node + 1] += lazy[node];
      }
      lazy[node] = 0;
    }
  }
  void update(long long idx, long long diff) {
    update(root, 0, n - 1, idx, diff);
  }
  void update(long long node, long long start, long long end, long long idx,
              long long diff) {
    if (start == end)
      tree[node] += diff;
    else {
      long long mid = (start + end) / 2;
      if (start <= idx && idx <= mid)
        update(2 * node, start, mid, idx, diff);
      else
        update(2 * node + 1, mid + 1, end, idx, diff);
      tree[node] = function(tree[2 * node], tree[2 * node + 1]);
    }
  }
  void updateRange(long long l, long long r, long long diff) {
    updateRange(root, 0, n - 1, l, r, diff);
  }
  void updateRange(long long node, long long start, long long end, long long l,
                   long long r, long long diff) {
    if (start > end || start > r || end < l) return;
    pendingUpdate(node, start, end);
    if (start >= l && end <= r) {
      tree[node] += (end - start + 1) * diff;
      if (start != end) {
        lazy[2 * node] += diff;
        lazy[2 * node + 1] += diff;
      }
      return;
    }
    long long mid = (start + end) / 2;
    updateRange(2 * node, start, mid, l, r, diff);
    updateRange(2 * node + 1, mid + 1, end, l, r, diff);
    tree[node] = function(tree[2 * node], tree[2 * node + 1]);
  }
  long long query(long long l, long long r) {
    return query(root, 0, n - 1, l, r);
  }
  long long query(long long node, long long start, long long end, long long l,
                  long long r) {
    if (r < start || end < l) return 0;
    pendingUpdate(node, start, end);
    if (l <= start && end <= r) return tree[node];
    long long mid = (start + end) / 2;
    return function(query(2 * node, start, mid, l, r),
                    query(2 * node + 1, mid + 1, end, l, r));
  }
};
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, d;
  cin >> n >> d;
  vector<long long> arr(n);
  long long sum = 0;
  for (long long &x : arr) {
    cin >> x;
    sum += x;
    if (sum > d) {
      cout << "-1\n";
      return 0;
    }
  }
  SegmentTree st(arr);
  sum = 0;
  long long i = 0;
  long long counter = 0;
  for (long long &x : arr) {
    if (x == 0) {
      if (sum < 0) {
        long long largest = st.query(i, n - 1);
        sum += d - largest;
        st.updateRange(i, n - 1, d - largest);
        counter++;
      }
    } else {
      sum += x;
    }
    i++;
  }
  cout << counter << '\n';
  return 0;
}
