#include <bits/stdc++.h>
using namespace std;

const int N = 100005;

int i, n, a[N], d, rs, sum[N], sumx[N], curr, x;

int main() {
  ios_base::sync_with_stdio(0);

  cin >> n >> d;
  for(i = 1; i <= n; ++i) {
    cin >> a[i];
    sum[i] = sum[i - 1] + a[i];
  }
  for(i = n, sumx[n + 1] = -1e9 + 59; i; --i)
    sumx[i] = max(sum[i], sumx[i + 1]);

  for(i = 1; i <= n; ++i) {
    if(a[i]) curr += a[i];
    if(!a[i]) {
    	if(i == n) { if(curr < 0) ++rs; continue; }
      x = d - sumx[i + 1] + sum[i] - curr;
      if(curr < 0) curr = curr + x, ++rs;
      if(curr > d) curr = d;
      if(curr < 0) return cout << "-1\n", 0;
    }
    if(curr > d) return cout << "-1\n", 0;
  }

  cout << rs << '\n';

  return 0;
}