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;
void swap(long long* a, long long* b) {
  long long temp = *a;
  *a = *b;
  *b = temp;
}
struct no {
  long long sum, maxpre;
};
no t[4 * 100005];
void build(long long a[], long long v, long long st, long long en) {
  if (st == en) {
    t[v].sum = a[st];
    t[v].maxpre = a[st];
  } else {
    long long md = (st + en) / 2;
    build(a, 2 * v, st, md);
    build(a, 2 * v + 1, md + 1, en);
    t[v].sum = t[2 * v].sum + t[2 * v + 1].sum;
    t[v].maxpre = max(t[2 * v].maxpre, t[2 * v].sum + t[2 * v + 1].maxpre);
  }
}
no qry(long long v, long long st, long long en, long long l, long long r) {
  no res;
  res.sum = res.maxpre = 0 - 1000000007;
  if (st > r || en < l) {
    return res;
  }
  if (st >= l && en <= r) {
    return t[v];
  }
  long long md = (st + en) / 2;
  if (l > md) {
    return qry(2 * v + 1, md + 1, en, l, r);
  }
  if (r <= md) {
    return qry(2 * v, st, md, l, r);
  }
  no lf = qry(2 * v, st, md, l, r);
  no rg = qry(2 * v + 1, md + 1, en, l, r);
  res.sum = lf.sum + rg.sum;
  res.maxpre = max(lf.maxpre, lf.sum + rg.maxpre);
  return res;
}
int32_t main() {
  long long n, d;
  cin >> n >> d;
  long long a[n + 1];
  for (long long i = 1; i <= n; i++) cin >> a[i];
  build(a, 1, 1, n);
  long long sm = 0, days = 0;
  bool flag = true;
  for (long long i = 1; i <= n; i++) {
    if (a[i] == 0) {
      if (sm >= 0)
        ;
      else {
        long long mnm = qry(1, 1, n, i, n).maxpre;
        if (mnm < 0)
          ;
        else if (mnm > d) {
          flag = false;
          break;
        } else {
          sm = max(0LL, d - mnm);
          days++;
        }
      }
    } else {
      sm += a[i];
    }
    if (sm > d) {
      flag = false;
      break;
    }
  }
  if (flag)
    cout << days << '\n';
  else
    cout << -1 << '\n';
}
