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.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.StringTokenizer;

public class Edu33D {
	
	public static void main(String[] args) {
		FS scan = new FS(System.in);
		int N = scan.nextInt();
		int D = scan.nextInt();
		
		int[] list = new int[N];
		for(int i=0;i<N;i++) {
			list[i] = scan.nextInt();
		}
		
		long sum = 0;
		long surplus = 0;
		int sol = 0;
		boolean valid = true;
		for(int i=0;i<N;i++) {
			if(list[i]==0) {
				if(sum < 0) {
					sum = D;
					sol ++;
					surplus = D;
				}else {
					surplus = Math.min(surplus, sum);
				}
			}else {
				sum+=list[i];
			}
			if(sum>D && sum - D <= surplus) {
				surplus-=sum - D;
				sum -= sum - D;
			}else if (sum > D ) {
				valid = false;
				break;
			}
		}
		System.out.println(valid?sol:-1);
	}
	private static class FS {
        BufferedReader br;
        StringTokenizer st;
        public FS(InputStream in) {
            br = new BufferedReader(new InputStreamReader(in));
        }
        String next(){
            while(st==null||!st.hasMoreElements()){
                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());}
    }
}