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


/**
 * gl hf
 */
public class Main {
    static class Task {
        PrintWriter out;



        public void solve(MyScanner in, PrintWriter out) {
            this.out = out;
            int currentMoney = 0;
            int n = in.nextInt();
            int d = in.nextInt();

            Integer[] values = new Integer[n];
            Integer[] input = new Integer[n];
            Arrays.fill(values, 0);
            int lastValue = 0;
            for (int i = 0; i < n; i++) {
                int a = in.nextInt();

                if (a == 0) {
                    values[i] = null;
                    input[i] = null;
                } else {
                    lastValue += a;
                    values[i] = lastValue;
                    input[i] = a;
                }
            }

            Integer[] maximum = new Integer[n];
            maximum[n - 1] = values[n - 1];
            for (int i = n - 2; i >= 0; i--) {
                Integer nextMax = maximum[i + 1];
                if (nextMax == null) {
                    maximum[i] = values[i];
                } else {
                    int thisValue = values[i] == null ? Integer.MIN_VALUE : values[i];
                    maximum[i] = Math.max(nextMax, thisValue);
                }
            }

            int delta = 0;
            int ct = 0;
            boolean err = false;
            lastValue = 0;
            for (int i = 0; i < n; i++) {
               // System.out.println("i = " + i + ", input = " + input[i] + ", lastVal = " + lastValue);
                if (input[i] == null && lastValue < 0) {
                    // need to lift up as much as we can
                    ct++;

                    if (maximum[i] == null) { //no more numbers, just get to 0 level, win
                       // System.out.println("Up by wahtever");
                        break;
                    }

                    //maximum real number
                    int realMax = delta + maximum[i];
                    //System.out.println("Current observed maximum: " + maximum[i] + " + " + delta + " = " + realMax);
                    if (realMax > d) {
                        //System.out.println("Exceeds possible max we meessed up");
                        err = true;
                        break;
                    }

                    lastValue += (d - realMax);
                    delta += (d - realMax);

                    if (lastValue < 0) {
                      //  System.out.println("Can't lift enough!");
                        err = true;
                        break;
                    }
                    //System.out.println("Up by " + (d - realMax) + ", last value = " + lastValue);
                } else {
                    //System.out.println("No need to lift up, input = " + input[i]);
                    if (input[i] != null) {
                        lastValue += input[i];
                      //  System.out.println("Last value " + lastValue);
                        if (lastValue > d) {
                            err = true;
                            break;
                        }
                    }
                }
            }
/*
            for (int i = 0; i < n; i++) {
                System.out.print(values[i] + " ");
            }
            System.out.println("");
            for (int i = 0; i < n; i++) {
                System.out.print(maximum[i] + " ");
            }
            System.out.println("");*/

            if (err) {
                out.println(-1);
            } else {
                out.println(ct);
            }
        }

    }

    public static void main(String[] args) {
        MyScanner in = new MyScanner();
        PrintWriter out = new PrintWriter(System.out);
        Task solver = new Task();
        solver.solve(in, out);
        out.close();
    }

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        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());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}