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.util.*;
import java.math.*;
import java.awt.Point;

public class Main {
    InputStream is;
    PrintWriter out;
    String INPUT = "";

    long MOD = 1_000_000_007;
    int inf = 10000000;
    void solve()
    {
        int n = ni();
        int d = ni();
        int[] a = new int[n];
        int[] b = new int[n];
        for(int i = 0; i < n; i++){
            a[i] = ni();
            if(i==0) b[i] = a[i];
            else b[i] = b[i-1] + a[i];
        }
        for(int i = 0; i < n; i++){
            if(b[i]>d){
                out.println(-1);
                return;
            }
        }
        int s = 0;
        int c = 0;
        int max = 2000000000;
        int[] p = new int[n];
        int t = 0;
        long ans = 0;
        for(int i = n-1; i >= 0; i--){
            p[i] = Math.min(d-b[i], max);
            max = p[i];
        }
        for(int i = 0; i < n; i++){
            if(a[i]==0){
                int x = b[i]+t;
                if(x<0){
                    t = p[i];
                    x = b[i]+t;
                    ans++;
                }
                if(x<0){
                    out.println(-1);
                    return;
                }
            }
        }
        out.println(ans);
    }

    public static class UnionFind{  
        int parent[];
        int rank[];
        
        public UnionFind(int n){
            parent = new int[n];
            rank   = new int[n];
            
            for(int i = 0;i < n;i++){
                parent[i] = i;
                rank[i]   = 0;
            }        
        }
        
        boolean same(int x,int y){
            return find(x) == find(y);
        }
        
        public int find(int x){
            if(parent[x] == x){
               return x;
            }else{
               return parent[x] = find(parent[x]);   
            }        
        }
          
        public void union(int x,int y){
            x = find(x);
            y = find(y);
            
            if(x != y){
                if(rank[x] > rank[y]){
                   parent[y] = x; 
                }else{
                   parent[x] = y;
                   if(rank[x] == rank[y]){
                       rank[y]++;
                   }
                }            
            }
            
            return;
        }
        
        public int count(int n){
            int ret = 0;
            for(int i = 0;i < n;i++){
                if(i == find(i)){
                    ret++;
                }
            }
            return ret;
        }
          
      } 
   
    void run() throws Exception
    {
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);
        
        long s = System.currentTimeMillis();
        solve();
        out.flush();
        if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
    }
    
    public static void main(String[] args) throws Exception { new Main().run(); }
    
    private byte[] inbuf = new byte[1024];
    private int lenbuf = 0, ptrbuf = 0;
    
    private int readByte()
    {
        if(lenbuf == -1)throw new InputMismatchException();
        if(ptrbuf >= lenbuf){
            ptrbuf = 0;
            try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
            if(lenbuf <= 0)return -1;
        }
        return inbuf[ptrbuf++];
    }
    
    private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
    private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
    
    private double nd() { return Double.parseDouble(ns()); }
    private char nc() { return (char)skip(); }
    
    private String ns()
    {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while(!(isSpaceChar(b) && b != ' ')){
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    
    private char[] ns(int n)
    {
        char[] buf = new char[n];
        int b = skip(), p = 0;
        while(p < n && !(isSpaceChar(b))){
            buf[p++] = (char)b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }
    
    private char[][] nm(int n, int m)
    {
        char[][] map = new char[n][];
        for(int i = 0;i < n;i++)map[i] = ns(m);
        return map;
    }
    
    private int[] na(int n)
    {
        int[] a = new int[n];
        for(int i = 0;i < n;i++)a[i] = ni();
        return a;
    }
    
    private int ni()
    {
        int num = 0, b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private long nl()
    {
        long num = 0;
        int b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }

    static class ArrayUtils {
        public static void fill(double[][] array, double value) {
            for (double[] a : array) Arrays.fill(a, value);
        }
 
        public static void fill(double[][][] array, double value) {
            for (double[][] l : array) fill(l, value);
        } 
    }
}
