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>
enum { WHITE, GREY, BLACK };
using namespace std;
long long int inf = 1e18;
template <class T>
T gcd(T a, T b) {
  return b == 0 ? a : gcd(b, a % b);
}
template <typename T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <typename T>
T last_bit(T n) {
  return n & 1;
}
template <class T>
T big_mod(T n, T p, T m) {
  if (p == 0) return (T)1;
  T x = big_mod(n, p / 2, m);
  x = (x * x) % m;
  if (p & 1) x = (x * n) % m;
  return x;
}
template <class T>
T modInv(T a, T m) {
  T x, y;
  extgcd(a, m, x, y);
  x %= m;
  while (x < 0) {
    x += m;
  }
  return x;
}
template <class T>
T extgcd(T a, T b, T& x, T& y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  } else {
    int g = extgcd(b, a % b, y, x);
    y -= a / b * x;
    return g;
  }
}
template <class T>
T multiplication(T n, T p, T m) {
  if (p == 0) return (T)0;
  T x = multiplication(n, p / 2, m);
  x = (x + x) % m;
  if (p & 1) x = (x + n) % m;
  return x;
}
template <class T>
T my_pow(T n, T p) {
  if (p == 0) return 1;
  T x = my_pow(n, p / 2);
  x = (x * x);
  if (p & 1) x = (x * n);
  return x;
}
template <class T>
double getdist(T a, T b) {
  return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}
template <class T>
T extract(string s, T ret) {
  stringstream ss(s);
  ss >> ret;
  return ret;
}
template <class T>
string tostring(T n) {
  stringstream ss;
  ss << n;
  return ss.str();
}
template <class T>
T Mod(T n, T m) {
  return (n % m + m) % m;
}
template <class T>
T MIN3(T a, T b, T c) {
  return min(a, min(b, c));
}
template <class T>
T MAX3(T a, T b, T c) {
  return max(a, max(b, c));
}
template <class T>
void print_vector(T& v) {
  int sz = v.size();
  if (sz) cout << v[0];
  for (int i = 1; i < sz; i++) cout << ' ' << v[i];
  cout << "\n";
}
bool isVowel(char ch) {
  ch = toupper(ch);
  if (ch == 'A' || ch == 'U' || ch == 'I' || ch == 'O' || ch == 'E')
    return true;
  return false;
}
bool isConsonant(char ch) {
  if (isalpha(ch) && !isVowel(ch)) return true;
  return false;
}
template <class R>
R Josephus(R n, R k) {
  R ans = 1;
  for (R i = 2; i <= n; i++) ans = (ans + k - 1) % i + 1;
  return ans;
}
template <class R>
R toitent_Phi2(R a) {
  R result = a;
  for (R i = 2; i * i <= a; i++) {
    if (a % i == 0) result = result - result / i;
    while (a % i == 0) a = a / i;
  }
  if (a > 1) result = result - result / a;
  return result;
}
template <typename T>
T Angle(T x1, T y1, T x2, T y2) {
  return atan(double(y1 - y2) / double(x1 - x2));
}
long long int a[100009];
int main() {
  cin.sync_with_stdio(false);
  cin.tie();
  ;
  long long int T, t;
  long long int i, j, k;
  long long int n, m, q;
  cin >> n >> q;
  long long int x = 0;
  for (i = 1; i <= n; i++) {
    cin >> a[i];
    x += a[i];
    if (a[i] == 0) {
      if (x < 0) x = 0;
    }
    if (x > q) {
      cout << "-1\n";
      return 0;
    }
  }
  long long int ans = 0;
  x = 0;
  for (i = 1; i <= n; i++) {
    x += a[i];
    if (a[i] == 0) {
      if (x < 0) {
        x = q;
        ans++;
      }
    }
    if (x > q) x = q;
  }
  cout << ans << "\n";
  return 0;
}
