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 <typename T>
T Abs(T x) {
  return x > 0 ? x : -x;
}
template <typename T>
T const& Max(T const& a, T const& b) {
  return a > b ? a : b;
}
template <typename T>
T const& Min(T const& a, T const& b) {
  return a < b ? a : b;
}
template <typename T>
inline T gcd(T a, T b) {
  return (b ? gcd(b, a % b) : a);
}
template <typename T>
T sqaa(T a) {
  return a * a;
}
long long int ar[MX], compress[MX];
int main() {
  long long int n, ans, d, cs;
  while (cin >> n >> d) {
    for (int i = 1; i <= n; i++) cin >> ar[i];
    cs = 1;
    long long int sum = ar[1];
    bool fl = 0, fl1 = 0, fl2 = 0;
    for (int i = 2; i <= n; i++) {
      if (ar[i - 1] < 0 && ar[i] < 0) {
        sum += ar[i];
      } else if (ar[i - 1] > 0 && ar[i] > 0) {
        sum += ar[i];
      } else if (ar[i - 1] == 0 && ar[i] == 0) {
        sum += 0;
      } else {
        compress[cs++] = sum;
        sum = ar[i];
      }
    }
    compress[cs] = sum;
    long long int ache = 0;
    bool valid = 1;
    int ans = 0;
    long long int barti_jug_korechi = 0;
    for (int i = 1; i <= cs; i++) {
      if (compress[i] == 0 && ache >= 0) {
        continue;
      } else if (compress[i] == 0) {
        ache = d;
        barti_jug_korechi = d;
        ans++;
      } else {
        ache += compress[i];
      }
      if (ache > d && ache - d <= barti_jug_korechi) {
        barti_jug_korechi -= ache - d;
        ache = d;
      } else if (ache > d) {
        valid = 0;
      }
    }
    if (!valid)
      cout << -1 << endl;
    else
      cout << ans << endl;
  }
  return 0;
}
