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.*;

public class main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        long d = in.nextLong();

        long splitTotal = 0;
        List<Integer> currentSplit = new ArrayList<>();

        boolean overshot = false;
        int deposits = 0;

        long previousSplitLeftover = 0;
        boolean previousSplitLeftoverUsable = false;

        boolean firstSplit = true;

        while (n-- > 0 && !overshot) {
            int day = in.nextInt();
            if (day == 0) {
                // Perform split checking
                if (splitTotal < 0) {
                    // See if no split is possible
                    if (previousSplitLeftoverUsable && previousSplitLeftover + splitTotal >= 0) {
                        // leftover from previous split is able to cover. check if there is any overshoot
                        long total = previousSplitLeftover + splitTotal;
                        for (int i = 0; i < currentSplit.size(); i++) {
                            total = total + currentSplit.get(i);
                            if (total > d || currentSplit.get(i) > d) {
                                overshot = true;
                                break;
                            }
                        }
                        // checking is done, we are able to skip this split's deposit
                        previousSplitLeftover = total;
                        previousSplitLeftoverUsable = true;
                    } else if (previousSplitLeftoverUsable) {
                        // there is leftover from previous split, but is not enough to cover. deposit needs to happen for this split
                        // also need to check for overshoot
                        long total = previousSplitLeftover;
                        for (int i = 0; i < currentSplit.size(); i++) {
                            total = total + currentSplit.get(i);
                            if (total > d || currentSplit.get(i) > d) {
                                overshot = true;
                                break;
                            }
                        }
                        deposits = deposits + 1;
                        previousSplitLeftoverUsable = false;
                    } else {
                        // there is no leftover from previous split. check if we can use previous split's deposit to go past this split without deposit
                        long total = -splitTotal;
                        boolean possible = true;
                        for (int i = 0; i < currentSplit.size(); i++) {
                            total = total + currentSplit.get(i);
                            if (total > d) {
                                possible = false;
                                break;
                            }
                        }
                        if (!possible || firstSplit) {
                            deposits = deposits + 1;
                        }
                        previousSplitLeftoverUsable = false;
                    }
                } else {
                    previousSplitLeftover = splitTotal;
                    previousSplitLeftoverUsable = true;
                }

                // Finished split operations, reset both variables
                splitTotal = 0;
                currentSplit = new ArrayList<>();
                firstSplit = false;
            } else {
                currentSplit.add(day);
                splitTotal = splitTotal + day;

                // check for overshoot
                if (day > d || splitTotal > d) {
                    overshot = true;
                    break;
                }
            }
        }

        if (overshot) {
            System.out.println(-1);
        } else {
            System.out.println(deposits);
        }

        in.close();
    }
}