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.*;
import java.lang.*;
import java.math.*;
import java.util.*;

public class D2 {
	public static void main(String[] args) {
		FastReader fr = new FastReader();
		int n = fr.nextInt();
		int d = fr.nextInt();
		int[] ia = new int[n];
		int[] presum = new int[n];
		ia[0] = fr.nextInt();
		presum[0] = ia[0];
		if(presum[0] > d){
			System.out.println(-1);
			return;
		}
		for(int i = 1; i < n; i++){
			ia[i] = fr.nextInt();
			presum[i] = presum[i-1]+ia[i];
			if(presum[i] > d){
				System.out.println(-1);
				return;
			}
		}
		int[] maxdepo = new int[n];
		maxdepo[n-1] = presum[n-1];
		for(int i = n-2; i >= 0; i--){
			maxdepo[i] = Math.max(maxdepo[i+1], presum[i]);
		}
		for(int i = 0; i < n; i++){
			maxdepo[i] = d-maxdepo[i];
		}
		int v = 0;
		int depo = 0;
		for(int i = 0; i < n; i++){
			if(ia[i] == 0 && presum[i] + depo < 0){
				int t = -1*(presum[i] + depo);
				if(t > maxdepo[i]+depo){
					System.out.println(-1);
					return;
				}
				depo=maxdepo[i];
				v++;
			}
		}
		System.out.println(v);
	}
}

class FastReader{
	BufferedReader br;
	StringTokenizer st;

	FastReader(){
		br = new BufferedReader(new InputStreamReader(System.in));
	}

	String next(){
		while(st==null || !st.hasMoreTokens()){
			try{
				st = new StringTokenizer(br.readLine());
			}catch(IOException e){
				e.printStackTrace();
			}
		}
		return st.nextToken();
	}

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

	long nextLong(){
		return Long.parseLong(next());
	}

	double nextDouble(){
		return Double.parseDouble(next());
	}

	String nextLine(){
		String str = "";
		try{
			str = br.readLine();
		}catch(IOException e){
			e.printStackTrace();
		}
		return str;
	}
}

//source: http://www.geeksforgeeks.org/fast-io-in-java-in-competitive-programming/