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;
template <typename T>
void MACRO_VAR_Scan(T& t) {
  cin >> t;
}
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First& first, Rest&... rest) {
  cin >> first;
  MACRO_VAR_Scan(rest...);
}
template <typename T>
void MACRO_VEC_ROW_Init(int n, T& t) {
  t.resize(n);
}
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Init(int n, First& first, Rest&... rest) {
  first.resize(n);
  MACRO_VEC_ROW_Init(n, rest...);
}
template <typename T>
void MACRO_VEC_ROW_Scan(int p, T& t) {
  cin >> t[p];
}
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Scan(int p, First& first, Rest&... rest) {
  cin >> first[p];
  MACRO_VEC_ROW_Scan(p, rest...);
}
void _main();
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}
template <class T>
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T>
inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <typename A, typename B>
inline void chmin(A& a, B b) {
  if (a > b) a = b;
}
template <typename A, typename B>
inline void chmax(A& a, B b) {
  if (a < b) a = b;
}
long long qp(long long a, long long b) {
  long long ans = 1ll;
  do {
    if (b & 1) ans = 1ll * ans * a;
    a = 1ll * a * a;
  } while (b >>= 1);
  return ans;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
inline bool valid(int x, int h) { return 0 <= x && x < h; }
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = (int)(1e9) + 7;
const long long MOD = (long long)(1e9) + 7;
const long long MOD2 = (long long)(1e18) + 9;
const long long INF2 = (long long)(1e18);
const long long INTMAX = (0x7FFFFFFFL);
const long long LLMAX = (0x7FFFFFFFFFFFFFFFL);
const int N4 = (int)1e4 + 10;
const int N5 = (int)1e5 + 10;
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, -1, -1, 1, 1};
long long ans, cur, cnt, sum, f, ret;
void _main() {
  int n;
  MACRO_VAR_Scan(n);
  ;
  long long d;
  MACRO_VAR_Scan(d);
  ;
  vector<long long> v(n);
  for (auto& i : v) cin >> i;
  ;
  for (int i = (0); i < (n); ++i) {
    if (v[i] == 0 && cur < 0) {
      cur = 0;
      ret++;
    }
    if (cur > d) {
      cout << -1 << endl;
      ;
      return;
    }
    cur += v[i];
    if (cur > d) {
      cout << -1 << endl;
      ;
      return;
    }
  }
  cout << ret << endl;
  ;
}
