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.*;
import java.lang.*;
import java.io.*;

/*
 * 
 * Comments Here
 * 
 */
public class E33D
{
	static BufferedReader br; 
	static BufferedWriter bw; 
	static StringTokenizer st;
	static FileReader fr;

	public static void main(String[] args) throws java.lang.Exception
	{
		bw = new BufferedWriter(new OutputStreamWriter(System.out));
		/**/
		br = new BufferedReader(new InputStreamReader(System.in));
    		/*/
    		File file = new File("src/in.txt");
		fr = new FileReader(file);
		/**/
		
		st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int d = Integer.parseInt(st.nextToken());
		
		long[] b = new long[n+1];
		
		st = new StringTokenizer(br.readLine());
		for(int i = 1; i <= n; ++i){
			b[i] = b[i-1]+Long.parseLong(st.nextToken());
		}
		
		
		long[] minc = new long[n+1];
		long[] maxc = new long[n+1];
		
		maxc[0] = d;
		
		for(int i = 1; i <= n; ++i){
			
			maxc[i] = d-b[i];
			
			if(b[i] == b[i-1]) {
				
				minc[i] = Math.max(0L, 0L-b[i]);
				
			} 
			
			
		}
		
		for(int i = 1; i <= n; ++i) {
			minc[i] = Math.max(minc[i], minc[i-1]);
		}
		
		for(int i = n-1; i >= 0; --i) {
			maxc[i] = Math.min(maxc[i], maxc[i+1]);
		}
		

		
		for(int i = 0; i <= n; ++i) {
			if(maxc[i] < minc[i]){
				bw.write("-1\n");
				bw.close();
				br.close();
				return;
			}
		}
		
		int trans = 0;
		long val = 0L;
		
		for(int i = 0; i <= n; ++i) {
			if(val < minc[i]) {
				++trans;
				val = maxc[i];
			}
		}
		
		bw.write(trans+"\n");
		
		
//		bw.write(Arrays.toString(b) + "\n");
//		bw.write(Arrays.toString(minc) + "\n");
//		bw.write(Arrays.toString(maxc) + "\n");
		
		br.close();
		bw.close();
	}
	

	
	
}

