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.Scanner;

public class CreditCard {

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int lim = sc.nextInt();
		long[] a = new long[n];
		long[] stan = new long[n];
		
		for(int i = 0; i < n; i++)
			a[i] = sc.nextInt();
		
		stan[0] = a[0]; //stan: amount of money per day if we didn't deposit at all.
		for(int i = 1; i < n; i++)
			stan[i] = stan[i-1] + a[i]; 
		
		long[] maxfrom = new long[n]; //max of stan from i onwards, for each i.
		//this is used to determine how much money we can deposit at a given day,
		//without triggering an over-limit at a later date.
		maxfrom[n-1] = stan[n-1];
		for(int i = n-2; i >= 0; i--)
			maxfrom[i] = Math.max(maxfrom[i+1], stan[i]);
		
		long money = 0;
		long offset = 0;
		int times = 0;
		for(int i = 0; i < n; i++)
		{
			money += a[i];
			
			if(money > lim)
			{
				System.out.println(-1);
				return;
			}
			
			if(a[i] == 0 && money + offset < 0)
			{
				//we need to add at least -(money+offset), but we want to add as much as possible
				//max amount that we can add, without exceeding any limit ahead:
				long add = lim - (maxfrom[i] + offset); 
				if(add < -(money+offset))
				{ //if that's not enough to make balance non-negative, resign.
					System.out.println(-1);
					return;
				}
				//add "add" amount of money
				offset += add;
				times++;
			}
		}
		System.out.println(times);
	}

}
