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 int MAXN = 1e5 + 100;
int n, d, t1, ar[MAXN], ans;
long long int amo = 0, maxi = -1e18;
vector<int> check;
set<pair<int, int> > ch;
vector<long long int> checkm1, checkmax1;
vector<long long int> checkm, checkmax;
void fastscan(int &x) {
  bool neg = false;
  register int c;
  x = 0;
  c = getchar();
  if (c == '-') {
    neg = true;
    c = getchar();
  }
  for (; (c > 47 && c < 58); c = getchar()) x = (x << 1) + (x << 3) + c - 48;
  if (neg) x *= -1;
}
int main() {
  ios::sync_with_stdio(false);
  fastscan(n);
  fastscan(d);
  check.push_back(-1);
  for (int i = 0; i < n; i++) {
    fastscan(ar[i]);
    if (ar[i] == 0) check.push_back(i);
  }
  check.push_back(n);
  for (int i = 0; i < check.size() - 1; i++) {
    amo = 0;
    maxi = -1e18;
    ch.insert(make_pair(check[i], i));
    for (int j = check[i] + 1; j < check[i + 1]; j++) {
      amo += ar[j];
      maxi = max(maxi, amo);
      if (maxi > d) {
        cout << -1;
        return 0;
      }
    }
    if (maxi == -1e18) maxi = 0;
    checkmax1.push_back(maxi);
    checkm1.push_back(amo);
  }
  long long int jj = 0;
  maxi = -1e18;
  for (int i = checkm1.size() - 1; i >= 0; i--) {
    jj += checkm1[i];
    if (i != checkm1.size() - 1) {
      checkm.insert(checkm.begin(), jj);
      maxi = max(maxi, checkmax1[i]);
      checkmax.insert(checkmax.begin(), maxi);
    } else {
      checkm.push_back(jj);
      maxi = max(maxi, checkmax1[i]);
      checkmax.push_back(maxi);
    }
  }
  amo = 0;
  for (int i = 0; i < n; i++) {
    amo += ar[i];
    if (ar[i] == 0) {
      set<pair<int, int> >::iterator it = ch.lower_bound(make_pair(i, 0));
      pair<int, int> T = *it;
      if (amo + checkm[T.second] > d || amo < 0) {
        ans++;
        maxi = -1e18;
        maxi = max(maxi, checkmax[T.second]);
        maxi = max(maxi, checkm[T.second]);
        if (d - maxi > d)
          amo = d;
        else
          amo = d - maxi;
      }
      if (amo < 0) {
        cout << -1;
        return 0;
      }
      if (amo > d - checkm[T.second]) {
        cout << -1;
        return 0;
      }
    }
  }
  cout << ans;
}
