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 long long int INF = 1e9 + 9;
const int MAX_N = 1e5 + 9;
int vec[MAX_N];
queue<int> que;
queue<int> qq;
int main() {
  int N, M, T;
  while (cin >> N >> M) {
    while (!que.empty()) que.pop();
    while (!qq.empty()) qq.pop();
    int cnt = 0, ant = 0;
    int x = INF;
    for (int i = 0; i < N; i++) {
      int t;
      scanf("%d", &t);
      cnt += t;
      int temp = M - t;
      x = min(x, temp);
      if (t == 0) {
        qq.push(x);
        que.push(cnt);
        cnt = 0;
        x = INF;
      }
    }
    qq.push(x);
    int sum = 0;
    int pos = 0;
    int ans = 0;
    while (!que.empty()) {
      int t = que.front();
      que.pop();
      qq.pop();
      if (t > M) {
        ans = -1;
        break;
      }
      sum += t;
      if (sum < 0) {
        if (sum + pos < 0) {
          ans++;
          pos += (qq.front() - sum);
        } else {
          pos -= sum;
        }
      } else if (sum > M) {
        ans = -1;
        break;
      }
    }
    if (cnt > M || cnt + sum > M) ans = -1;
    if (ans == -1)
      cout << "-1" << endl;
    else
      cout << ans << endl;
  }
  return 0;
}
