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

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        FastScanner in = new FastScanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        new Main().run(in, out);
        out.close();
    }

    public static long mod = 17352642619633L;

    void run(FastScanner in, PrintWriter out) {

        int N = in.nextInt();
        long D = in.nextInt();

        long[] a = new long[N];
        for (int i = 0; i < N; i++) a[i] = in.nextLong();

        long[] bal = new long[N];
        long b = 0;
        for (int i = 0; i < N; i++) {
            b += a[i];
            bal[i] = b;
        }

        MaxStack ms = new MaxStack();
        ms.add((long) -1e11);
        for (int i = N-1; i >= 0; i--) {
            ms.add(bal[i]);
        }

        if (ms.max() > D) {
            out.println("-1");
            return;
        }

        // System.out.println(Arrays.toString(bal));

        int ret = 0;
        int delta = 0;
        for (int i = 0; i < N; i++) {
            if (a[i] == 0) {
                if (bal[i] + delta >= 0) continue;
                // how much can we add
                long canadd = D - (ms.max()+delta);
                if (canadd < 0 || bal[i] + canadd + delta < 0) {
                    out.println("-1");
                    return;
                }
                delta += canadd;
                ret++;
            }
            ms.pop(bal[i]);
        }

        out.println(ret);
    }


    class MaxStack {
        LinkedList<Long> ll = new LinkedList<>();
        void add(long x) {
            if (ll.isEmpty() || x >= ll.peekLast()) {
                ll.offerLast(x);
            }
        }

        void pop(long x) {
            if (ll.peekLast() == x) ll.pollLast();
        }

        long max() {
            return ll.peekLast();
        }

    }

    static class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        public FastScanner(InputStream in) {
            br = new BufferedReader(new InputStreamReader(in));
            st = null;
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}
