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 tint = long long;
using ld = long double;
using vi = vector<int>;
using vl = vector<tint>;
using vb = vector<bool>;
using pi = pair<int, int>;
using pl = pair<tint, tint>;
const int MOD = 1e9 + 7;
const int mod = 998244353;
const int MX = 3e5 + 5;
const tint INF = 1e18;
const int inf = 2e9;
const ld PI = acos(ld(-1));
const ld eps = 1e-8;
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, 1, -1};
template <class T>
void remDup(vector<T>& v) {
  sort(begin(v), end(v));
  v.erase(unique(begin(v), end(v)), end(v));
}
template <class T>
bool valid(T x, T y, T n, T m) {
  return (0 <= x && x < n && 0 <= y && y < m);
}
void NACHO(string name = "cbarn") {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
}
int main() {
  NACHO();
  int n, d;
  cin >> n >> d;
  vi a(n);
  for (int i = 0; i < int(n); i++) cin >> a[i];
  vi suff(n);
  suff[n - 1] = a[n - 1];
  for (int i = n - 2; i >= 0; --i) {
    suff[i] = max(suff[i + 1], a[i]);
  }
  int cur = 0;
  int ret = 0;
  bool ok = 1;
  for (int i = 0; i < int(n); i++) {
    if (a[i] == 0) {
      if (cur < 0) {
        ++ret;
        cur = min(d, max(0, d - suff[i]));
      }
    } else {
      cur += a[i];
      if (cur > d) ok = 0;
    }
  }
  if (!ok) ret = -1;
  cout << ret << "\n";
}
