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 ll = long long;
template <typename t>
using V = vector<t>;
template <typename t>
void print(ostream& os, const t& a) {
  os << a << '\n';
}
template <typename t, typename... A>
void print(ostream& os, const t& a, A&&... b) {
  os << a << ' ';
  print(os, b...);
}
int n, d;
V<pair<int, int> > ilo;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n >> d;
  int cnt = 0;
  int maks = 0;
  for (int i = 0; i < n; ++i) {
    int a;
    cin >> a;
    if (a == 0) {
      ilo.push_back({cnt, maks});
      cnt = 0;
      maks = 0;
    } else {
      cnt += a;
      maks = max(maks, cnt);
    }
  }
  ilo.push_back({cnt, maks});
  ;
  cnt = 0;
  int pt = 0;
  for (; pt < ilo.size(); ++pt) {
    if (cnt + ilo[pt].second > d) return print(cout, -1), 0;
    cnt += ilo[pt].first;
    if (cnt < 0) break;
    if (cnt > d) return print(cout, -1), 0;
  }
  if (pt == ilo.size()) return print(cout, 0), 0;
  if (pt == ilo.size() - 1) return print(cout, -1), 0;
  ;
  int res = 1;
  int lo = 0;
  int hi = d;
  for (int i = pt + 1; i < ilo.size(); ++i) {
    hi = min(hi, d - ilo[i].second);
    hi += ilo[i].first;
    hi = min(hi, d);
    lo += ilo[i].first;
    if (lo > hi) return print(cout, -1), 0;
    if (hi < 0) {
      if (i == ilo.size() - 1) break;
      ++res;
      lo = 0, hi = d;
    }
    lo = max(0, lo);
    ;
  }
  print(cout, res);
}
