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

//package cow17;
/*
LANG: JAVA
TASK: 
*/

import java.io.*;
import java.util.*;
public class cf4
{
	public static void main(String[] args) throws IOException
	{
		Scanner c = new Scanner(System.in);
		int N = c.nextInt(), D = c.nextInt();
		int[] arr = new int[N];
		for(int i=0; i<N; i++) arr[i] = c.nextInt();
		long[] pre = new long[N];
		pre[0] = arr[0];
	
		for(int i=1; i<N; i++) 
		{
			pre[i] = pre[i-1] + arr[i];
			if(pre[i] > D)
			{
				System.out.println(-1); return;
			}
		}
		
		long[] maxPre = new long[N];
		maxPre[N-1] = pre[N-1];
		for(int i=N-2; i>=0; i--)
		{
			maxPre[i] = Math.max(maxPre[i+1], pre[i]);
		}
		
		long curSum = 0; int count = 0;
		for(int i=0; i<N; i++)
		{
			curSum += arr[i];
			if(arr[i] == 0 && curSum < 0)
			{
				long flood = maxPre[i] - pre[i];
				long add = D-(curSum+flood); 
				curSum += add; count++;
			}
		}
		System.out.println(count);
	}
}
