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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.Solve(in, out);
        out.close();
    }


    static class TaskC {


        public void Solve(InputReader in, PrintWriter out) {
            int n = in.NextInt();
            int d = in.NextInt();
            int[] a = in.NextIntArray(n);
            int[] dp = new int[n + 1];
            for (int i = 0; i < n; i++) {
                dp[i + 1] = dp[i] + a[i];
            }
            int[] maxDpUntilEnd = new int[n + 1];
            maxDpUntilEnd[n] = dp[n];
            for (int i = n - 1; i >= 0; i--) {
                maxDpUntilEnd[i] = Math.max(maxDpUntilEnd[i + 1], dp[i]);
            }
            if (maxDpUntilEnd[0] > d) {
                out.println(-1);
                return;
            }
            int addedBalance = 0;
            int minTimes = 0;
            for (int i = 0; i < n; i++) {
                if (dp[i + 1] + addedBalance < 0 && a[i] == 0) {
                    addedBalance = d - maxDpUntilEnd[i + 1];
                    if (dp[i + 1] + addedBalance < 0) {
                        out.println(-1);
                        return;
                    } else {
                        minTimes++;
                    }
                }
            }
            out.println(minTimes);
        }
    }


    public static int GetMax(int[] ar) {
        int max = Integer.MIN_VALUE;
        for (int a : ar) {
            max = Math.max(max, a);
        }
        return max;
    }

    public static int GetMin(int[] ar) {
        int min = Integer.MAX_VALUE;
        for (int a : ar) {
            min = Math.min(min, a);
        }
        return min;
    }

    public static long GetSum(int[] ar) {
        long s = 0;
        for (int a : ar) s += a;
        return s;
    }

    public static int[] GetCount(int[] ar) {
        return GetCount(ar, GetMax(ar));
    }

    public static int[] GetCount(int[] ar, int maxValue) {
        int[] dp = new int[maxValue + 1];
        for (int a : ar) {
            dp[a]++;
        }
        return dp;
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String Next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine(), " \t\n\r\f,");
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int NextInt() {
            return Integer.parseInt(Next());
        }

        public long NextLong() {
            return Long.parseLong(Next());
        }

        public double NextDouble() {
            return Double.parseDouble(Next());
        }

        public int[] NextIntArray(int n) {
            return NextIntArray(n, 0);
        }

        public int[] NextIntArray(int n, int offset) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = NextInt() - offset;
            }
            return a;
        }

        public int[][] NextIntMatrix(int n, int m) {
            return NextIntMatrix(n, m, 0);
        }

        public int[][] NextIntMatrix(int n, int m, int offset) {
            int[][] a = new int[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    a[i][j] = NextInt() - offset;
                }
            }
            return a;
        }
    }
}