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 LIM = 1e5 + 5, MOD = 1e9 + 7;
bool prime[11000];
void SieveOfEratosthenes(long long int n) {
  memset(prime, true, sizeof(prime));
  for (int p = 2; p * p <= n; p++) {
    if (prime[p] == true) {
      for (int i = p * p; i <= n; i += p) prime[i] = false;
    }
  }
}
long long int dp[1005][1005][2], a[1005][1005], n;
long long int f[500005];
int main() {
  long long int n, d;
  cin >> n >> d;
  long long int a[n + 5];
  for (long long int i = 0; i < n; i++) {
    cin >> a[i];
  }
  long long int k = 0;
  long long int t;
  long long int sum = 0;
  long long int i, j;
  for (i = -1; i < n;) {
    t = k;
    long long int max1 = -1e18;
    for (j = i + 1; 1; j++) {
      if (j == n) {
        break;
      }
      if (a[j] == 0) {
        break;
      }
      t = t + a[j];
      max1 = max(max1, t);
    }
    if (j == n) {
      if (k >= 0) {
        if (max1 > d) {
          cout << -1;
          return 0;
        }
      } else {
        if (max1 > d) {
          cout << -1;
          return 0;
        } else {
          sum++;
          break;
        }
      }
    }
    if (d - max1 > 0 and k < 0 and i != -1 and j != n) {
      sum++;
      t += (d - max1);
    }
    if (d - max1 < 0 and k < 0 and i != -1 and j != n) {
      cout << -1;
      return 0;
    }
    i = j;
    k = t;
  }
  cout << sum;
}
