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 arr[800001];
long long tree[800001];
long long lazy[800001];
void buildtree(long long start, long long end, long long index) {
  if (start > end) {
    return;
  }
  if (start == end) {
    tree[index] = arr[start];
    return;
  }
  long long mid = (start + end) >> 1;
  buildtree(start, mid, 2 * index);
  buildtree(mid + 1, end, 2 * index + 1);
  tree[index] = max(tree[2 * index], tree[2 * index + 1]);
  return;
}
void updatelazy(long long start, long long end, long long index, long long val,
                long long low, long long high) {
  if (start > end) {
    return;
  }
  if (lazy[index] != -1) {
    tree[index] = max(tree[index], lazy[index]);
    if (start != end) {
      lazy[2 * index] = max(lazy[index], lazy[2 * index]);
      lazy[2 * index + 1] = max(lazy[index], lazy[2 * index + 1]);
    }
    lazy[index] = -1;
  }
  if (start > high || end < low) {
    return;
  }
  if (start >= low && end <= high) {
    tree[index] = val;
    if (start != end) {
      lazy[index] = val;
      lazy[2 * index] = max(lazy[index], lazy[2 * index]);
      lazy[2 * index + 1] = max(lazy[index], lazy[2 * index + 1]);
    }
    lazy[index] = -1;
    return;
  }
  long long mid = (start + end) >> 1;
  updatelazy(start, mid, 2 * index, val, low, high);
  updatelazy(mid + 1, end, 2 * index + 1, val, low, high);
  tree[index] = max(tree[2 * index], tree[2 * index + 1]);
  return;
}
long long getval(long long start, long long end, long long index, long long low,
                 long long high) {
  if (lazy[index] != -1) {
    tree[index] = max(tree[index], lazy[index]);
    if (start != end) {
      lazy[2 * index] = max(lazy[index], lazy[2 * index]);
      lazy[2 * index + 1] = max(lazy[index], lazy[2 * index + 1]);
    }
    lazy[index] = -1;
  }
  if (start > high || end < low) {
    return INT_MIN;
  }
  if (start >= low && end <= high) {
    tree[index] = max(tree[index], lazy[index]);
    if (start != end) {
      lazy[2 * index] = max(lazy[index], lazy[2 * index]);
      lazy[2 * index + 1] = max(lazy[index], lazy[2 * index + 1]);
    }
    lazy[index] = -1;
    return tree[index];
  }
  long long mid = (start + end) >> 1;
  return max(getval(start, mid, 2 * index, low, high),
             getval(mid + 1, end, 2 * index + 1, low, high));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t;
  t = 1;
  while (t--) {
    long long n, d;
    cin >> n >> d;
    vector<long long> v1;
    memset(lazy, -1, sizeof(lazy));
    for (long long i = 0; i < n; i++) {
      long long num;
      cin >> num;
      v1.push_back(num);
      if (i > 0) {
        arr[i] += arr[i - 1];
      }
      arr[i] += num;
    }
    arr[n] = INT_MIN;
    buildtree(0, n - 1, 1);
    long long used = 0;
    long long ans = 0;
    for (long long i = 0; i < n; i++) {
      if (v1[i] != 0) {
        continue;
      }
      if (v1[i] == 0 && arr[i] >= 0) {
        continue;
      }
      long long num = getval(0, n - 1, 1, i, n - 1);
      long long tmp = d - num - used;
      if (arr[i] + tmp + used < 0) {
        cout << "-1";
        return 0;
      }
      used += tmp;
      ans++;
    }
    cout << ans;
  }
  return 0;
}
