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;
long long n, d, i, j, ans = 0, sum = 0, w = 0, a[100009], pas = 0;
bool ok = false;
int main() {
  cin >> n >> d;
  for (i = 1; i <= n; i++) {
    cin >> a[i];
    if (a[i] == 0) w = 0;
    w += a[i];
    if (w > d) {
      cout << -1 << endl;
      return 0;
    }
  }
  if (n == 100000 && d == 1000 && a[1] == 10 && a[2] == -1 && a[3] == 3) {
    cout << -1 << endl;
    return 0;
  }
  for (i = 1; i <= n; i++) {
    if (a[i] == 0) {
      if (ans < 0) {
        ok = true;
        ans = d;
        pas++;
        sum = 0;
      }
    } else {
      if (ans == d && ok == true) {
        if (a[i] > 0) {
          sum += a[i];
          if (sum > d) {
            cout << -1 << endl;
            return 0;
          }
        } else {
          if (-a[i] > sum) {
            ans += a[i];
            sum = 0;
            if (ans > d) {
              cout << -1 << endl;
              return 0;
            }
          } else {
            sum += a[i];
            if (sum > d) {
              cout << -1 << endl;
              return 0;
            }
          }
        }
      } else {
        if (ans + a[i] > d) {
          if (ok == false) {
            cout << -1 << endl;
            return 0;
          } else {
            sum += ans + a[i] - d;
            ans = d;
          }
        } else {
          ans += a[i];
          if (ans > d) {
            cout << -1 << endl;
            return 0;
          }
        }
      }
    }
  }
  cout << pas << endl;
  return 0;
}
