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;
template <class T>
bool umin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
bool umax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
long long s[100009 << 2], lazy[100009 << 2], par[100009], arr[100009];
void build(int nd, int x, int y) {
  if (x == y) {
    s[nd] = par[x];
    return;
  }
  int mid = (x + y) >> 1;
  build(nd << 1, x, mid);
  build(nd << 1 | 1, mid + 1, y);
  s[nd] = max(s[nd << 1], s[nd << 1 | 1]);
}
void shift(int nd) {
  long long& ret = lazy[nd];
  if (!ret) return;
  s[nd << 1] += ret;
  lazy[nd << 1] += ret;
  s[nd << 1 | 1] += ret;
  lazy[nd << 1 | 1] += ret;
  ret = 0;
}
void inc(int l, int r, int v, int nd, int x, int y) {
  if (l > y or x > r) return;
  if (l <= x and y <= r) {
    lazy[nd] += v;
    s[nd] += v;
    return;
  }
  shift(nd);
  int mid = (x + y) >> 1;
  inc(l, r, v, nd << 1, x, mid);
  inc(l, r, v, nd << 1 | 1, mid + 1, y);
  s[nd] = max(s[nd << 1], s[nd << 1 | 1]);
}
long long get(int l, int r, int nd, int x, int y) {
  if (l > y or x > r) return -1000000000007;
  if (l <= x and y <= r) return s[nd];
  shift(nd);
  int mid = (x + y) >> 1;
  return max(get(l, r, nd << 1, x, mid), get(l, r, nd << 1 | 1, mid + 1, y));
}
int main() {
  int n, d;
  scanf("%d%d", &n, &d);
  for (int i = 1; i <= n; i++) {
    int x;
    scanf("%d", &x);
    par[i] = par[i - 1] + x;
    arr[i] = x;
  }
  build(1, 1, n);
  int p = 1, ans = 0;
  for (int i = 1; i <= n; i++)
    if (!arr[i]) {
      if (get(i, i, 1, 1, n) >= 0) continue;
      long long mx = -1000000000007, pos;
      for (int j = p; j < i; j++)
        if (umax(mx, d - (get(i, n, 1, 1, n)))) pos = j;
      inc(pos, n, mx, 1, 1, n);
      if (get(i, i, 1, 1, n) < 0) return puts("-1") * 0;
      ans++;
      p = i;
    }
  printf("%d\n", ans);
  return 0;
}
