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 Main {
	static int[] a=new int[100005];
	static int[] pre=new int[100005];
	static int[] max=new int[100005];
public static void main(String[] args){
	Scanner input=new Scanner(System.in);
	int n=input.nextInt();
	int d=input.nextInt();

	for(int i=1;i<=n;i++){
		a[i]=input.nextInt();
	}
	pre[0]=0;
	pre[0] = 0;  
    for(int i = 1; i <= n; ++i){  
        pre[i] = pre[i-1] + a[i];  
    }  
    max[n] = pre[n];  
    for(int i = n - 1; i >= 1; --i){  
        max[i]=Math.max(max[i+1],pre[i]);  
    }  
    long add = 0;  
    int ans = 0;  
    boolean test=true;
    for(int i =1;i<=n;i++){  
        if(a[i] == 0){  
            if(add+pre[i] < 0){  
                add+=d-(max[i]+add);  
                ans++;  
            }  
            if(add + pre[i] < 0){  
               System.out.println(-1);
               test=false;
            }  
        }  
        else{  
            if(add + pre[i] > d){  
               System.out.println(-1); 
               test=false;
            }  
        }  
    }  
    if(test){
    System.out.println(ans);
    }
}
}

    		 		 	  						 	 				   	