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.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;



public class CFE33D 
{
	
	
	public static int highestChange(int ind1, int ind2, int[]trans)
	{
		int highest = 0;
		int current = 0;
		for (int i=ind1+1;i<ind2;i++)
		{
			current += trans[i];
			if (current > highest)
			{
				highest = current;
			}
		}
		return highest;
	}
	
	static int MOD = 1000000000 + 7;
	public static int findNextCheckingDay(int ind, int[] trans)
	{
		for (int i=ind+1;i<trans.length;i++)
		{
			if (trans[i] == 0)
			{
				return i;
			}
		}
		return -1;
	}
	
	public static int findSumToNextCheckDay(int ind1, int ind2, int[] trans)
	{
		int sum = 0;
		for (int i=ind1+1;i<ind2;i++)
		{
			sum += trans[i];
		}
		return sum;
	}

	
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        
        int n = in.nextInt();       
        int lim = in.nextInt();
        int[] trans = new int[n];
        for (int i=0;i<n;i++)
        {
        	trans[i] = in.nextInt();
        }
        int res = 0;
        int currentBal = 0;
        for (int i=0;i<n;i++)
        {
        	int day = trans[i];
        	if (day == 0)
        	{
        		if (currentBal < 0)
        		{
        			res++;
        			int next = findNextCheckingDay(i,trans);
        			if (next != -1)
        			{
        				int x = findSumToNextCheckDay(i, next, trans);
        				if (x < 0 && highestChange(i,next,trans) <= lim + x)
        				{
        					currentBal = 0 - x;
        				}
        				else
        				{
        					currentBal = 0;
        				}
        			}
        			else
        			{
        				currentBal = 0;
        			}
        			
        			
        		}
        	}
        	else if (day < 0)
        	{
        		currentBal += day;
        	}
        	else
        	{
        		if (currentBal + day > lim)
        		{
        			res = -1;
        			break;
        		}
        		else
        		{
        			currentBal += day;
        		}
        	}
        }
        
        out.println(res);
        
        
        
       
        out.close();
    }

    
    
    
    
    
    
    
    
    
    
    
    
    
    
    

    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());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

    }
}