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 int INF = 1e16;
int arr[111111];
vector<int> ar[111111];
int main(void) {
  int n, m, ff = -1;
  scanf("%d%d", &n, &m);
  for (int e = 0; e < n; e++) scanf("%d", &arr[e]);
  for (int e = n - 1; e >= 0; e--) {
    if (arr[e] == 0)
      ff++;
    else if (ff >= 0) {
      ar[ff].push_back(arr[e]);
    }
  }
  for (int e = 0; e <= ff; e++) {
    reverse(ar[e].begin(), ar[e].end());
  }
  long long int tot = 0, kk = 0;
  for (int p = ff; p >= 0; p--) {
    long long int rr = tot;
    for (int e = 0; e < ar[p].size(); e++) {
      rr += ar[p][e];
      if (rr > m) rr = m;
    }
    if (rr >= 0) {
      tot = rr;
      continue;
    } else {
      rr = tot;
      for (int e = 0; e < ar[p].size(); e++) {
        rr += ar[p][e];
        if (rr > m) rr = m;
        if (rr < -m) {
          rr += m;
          kk++;
        }
      }
    }
    if (rr < 0) {
      if (rr < -m) {
        cout << "-1";
        return 0;
      } else {
        rr += m;
        kk++;
      }
    }
    tot = rr;
  }
  cout << kk;
  return 0;
}
