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;
inline istream& operator>>(istream& in, pair<long long, long long>& a) {
  return in >> a.first >> a.second;
}
inline ostream& operator<<(ostream& out, const pair<long long, long long>& a) {
  return out << a.first << ' ' << a.second;
}
struct SegmentTree {
  const long long Neutral = 1e18;
  vector<long long> tree, tadd;
  SegmentTree(long long val) : tree(4 * val), tadd(4 * val) {}
  void build(vector<long long>& value, long long v, long long tl, long long tr);
  long long query(long long l, long long r, long long v, long long tl,
                  long long tr);
  void update(long long l, long long r, long long value, long long v,
              long long tl, long long tr);
  void push(long long v, long long tl, long long tr) {
    tree[v] += tadd[v];
    if (tl != tr) {
      tadd[2 * v + 1] += tadd[v];
      tadd[2 * v + 2] += tadd[v];
    }
    tadd[v] = 0;
  }
  void recount(long long v) { tree[v] = min(tree[2 * v + 1], tree[2 * v + 2]); }
};
void SegmentTree::build(vector<long long>& value, long long v, long long tl,
                        long long tr) {
  if (tl == tr)
    tree[v] = value[tl];
  else {
    long long tm = (tl + tr) / 2;
    build(value, 2 * v + 1, tl, tm);
    build(value, 2 * v + 2, tm + 1, tr);
    recount(v);
  }
}
long long SegmentTree::query(long long l, long long r, long long v,
                             long long tl, long long tr) {
  push(v, tl, tr);
  if (tr < l || tl > r) return Neutral;
  if (tl >= l && tr <= r) return tree[v];
  long long tm = (tl + tr) / 2;
  long long q1 = query(l, r, 2 * v + 1, tl, tm),
            q2 = query(l, r, 2 * v + 2, tm + 1, tr);
  return min(q1, q2);
}
void SegmentTree::update(long long l, long long r, long long value, long long v,
                         long long tl, long long tr) {
  push(v, tl, tr);
  if (tr < l || tl > r) return;
  if (tl >= l && tr <= r) {
    tadd[v] = value;
    push(v, tl, tr);
    return;
  }
  long long tm = (tl + tr) / 2;
  update(l, r, value, 2 * v + 1, tl, tm);
  update(l, r, value, 2 * v + 2, tm + 1, tr);
  recount(v);
}
inline void Slove() {
  long long n = 0, d = 0;
  cin >> n >> d;
  vector<long long> data(n);
  for (auto& it : data) cin >> it;
  vector<long long> maximum, sum;
  long long value = 0, element = 0, ftp = 0;
  for (long long i = 0; i < n; i++) {
    if (data[i] == 0) {
      maximum.push_back(d - element);
      sum.push_back(value);
      value = 0;
    } else {
      ftp += data[i];
      value += data[i];
      element = max(element, value);
      if (value > d) {
        cout << -1;
        return;
      }
    }
  }
  long long sz = sum.size();
  SegmentTree check(sz), cherry(sz);
  check.build(maximum, 0, 0, sz - 1);
  cherry.build(sum, 0, 0, sz - 1);
  long long counter = 0;
  for (long long i = 0; i < sz; i++) {
    long long val = cherry.query(i, i, 0, 0, sz - 1);
    if (val < 0) {
      long long ans = check.query(i, sz - 1, 0, 0, sz - 1);
      if (ans < 0) {
        cout << -1;
        return;
      }
      cherry.update(i, sz - 1, ans, 0, 0, sz - 1);
      check.update(i, sz - 1, ans, 0, 0, sz - 1);
      counter++;
    }
  }
  cout << counter;
}
signed main() {
  ios_base::sync_with_stdio(false);
  Slove();
  return 0;
}
