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


/**
 * @author: Mehul Raheja
 */
import java.util.*;
import java.io.*;

public class CreditCard {

    /*
        Runtime = O()
     */
    static int N, M, K;
    static String s;
    static StringTokenizer st;
    static int[] d;

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        st = new StringTokenizer(br.readLine());
        int N = Integer.parseInt(st.nextToken());
        int M = Integer.parseInt(st.nextToken());
        st = new StringTokenizer(br.readLine());
        int[] d = new int[N];

        for (int p = 0; p < N; p++) {
            d[p] = Integer.parseInt(st.nextToken());
        }
        int cur = 0;
        int ans = 0;
        int[] pf = new int[N];
//        pf[0] = d[0];
//        for (int i = 1; i < N; i++) {
//            pf[i] = pf[i - 1] + d[i];
//        }
//        for (int i = N-2; i >= 0; i--) {
//            pf[i] = Math.max(pf[i], pf[i+1]);
//        }
        
        pf[N-1] = d[N-1];
        for (int i = N-2; i >= 0; i--) {
            pf[i] = pf[i+1] + ((d[i] > 0)?d[i]:0);
        }
        int[] next = new int[N];
        int last = N;
        for (int i = N - 1; i >= 0; i--) {
            next[i] = last;
            if (d[i] == 0) {
                last = i;
            }
        }
//        System.out.println(Arrays.toString(next));
//        System.out.println(Arrays.toString(pf));

        for (int i = 0; i < N; i++) {
            cur += d[i];
            //System.out.println("CURSTART = " + cur);
            if (cur > M) {
                System.out.println(-1);
                System.exit(0);
            }
            if (d[i] == 0) {

                int max = pf[i];
                //System.out.println("MAX");
//                if (max > M - Math.max(cur,0)) {
//                    System.out.println(-1);
//                    System.exit(0);
//                }
                
                if (cur < 0) {
                    cur = M - max;
                    if(cur < 0){
                        System.out.println(-1);
                       System.exit(0);
                    }
                    ans++;
                }
                //System.out.println("MAX = " + max);

            }
//            System.out.println("CUREND = " + cur);
//            System.out.println("");
        }
        
        //System.out.println("FINCUR = " + cur);
        System.out.println( ans);
    }
}

/*
int x = (int)Math.ceil((-1.0 * (double)cur)/M);
                    ans += x;
                    cur += M * x;
                    if(ans > i){
                        System.out.println(-1);
                        System.exit(0);
                    }
 */
