import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.StringTokenizer;

public class Main {
    private BufferedReader in;
    private StringTokenizer tok;
    private PrintWriter out;

    //------------------------------------------------------------------------------
    public static void main(String[] args) {
        new Main().run();
    }

    final static int INF = (int) 1e9;

    private void solve() throws IOException {
        int n = readInt();
        int k = readInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = readInt() - 1;
        }

        //noinspection unchecked
        List<Integer>[] positions = new List[k];
        for (int i = 0; i < k; i++) {
            positions[i] = new ArrayList<>();
        }
        for (int i = 0; i < n; i++) {
            positions[a[i]].add(i);
        }

        if (positions[0].isEmpty()) {
            out.println(0);
            return;
        }

        int[] dp = new int[n + 1];
        boolean[] parentIsRemoved = new boolean[n + 1];
        int[] parentPrevIndex = new int[n + 1];
        Arrays.fill(dp, INF);
        Arrays.fill(parentPrevIndex, -1);
        dp[positions[0].get(0)] = 0;
        for (int value = 0; value < k; value++) {
            for (int i = 0; i < positions[value].size(); i++) {
                int index = positions[value].get(i);

                {
                    int nextSameIndex;
                    if (i == positions[value].size() - 1) {
                        nextSameIndex = n;
                    } else {
                        nextSameIndex = positions[value].get(i + 1);
                    }
                    if (dp[nextSameIndex] > dp[index] + 1) {
                        dp[nextSameIndex] = dp[index] + 1;
                        parentIsRemoved[nextSameIndex] = true;
                        parentPrevIndex[nextSameIndex] = index;
                    }
                }

                if (value < k - 1) {
                    int bsPos = ~Collections.binarySearch(positions[value + 1], index);
                    int nextIncIndex;
                    if (bsPos == positions[value + 1].size()) {
                        nextIncIndex = n;
                    } else {
                        nextIncIndex = positions[value + 1].get(bsPos);
                    }
                    if (dp[nextIncIndex] > dp[index]) {
                        dp[nextIncIndex] = dp[index];
                        parentIsRemoved[nextIncIndex] = false;
                        parentPrevIndex[nextIncIndex] = index;
                    }
                }
            }
        }

        List<Integer> ans = new ArrayList<>();
        int now = n;
        //noinspection ConditionalBreakInInfiniteLoop
        while (true) {
            if (now == -1) {
                break;
            }
            if (parentIsRemoved[now]) {
                ans.add(parentPrevIndex[now]);
            }
            now = parentPrevIndex[now];
        }
        if (ans.size() != dp[n]) {
            throw new AssertionError();
        }

        Collections.sort(ans);
        out.println(ans.size());
        for (int index : ans) {
            out.print((index + 1) + " ");
        }
        out.println();
    }

    private void run() {
        try {
            initIO();
            solve();
            in.close();
            out.close();
        } catch (Throwable e) {
            throw new RuntimeException(e);
        }
    }

    @SuppressWarnings("RedundantThrows")
    private void initIO() throws IOException {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
//        in = new BufferedReader(new FileReader(new File("input.txt")));
//        out = new PrintWriter(new File("output.txt"));
    }

    private String readString() throws IOException {
        while (tok == null || !tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine());
        }
        return tok.nextToken();
    }

    @SuppressWarnings("unused")
    private int readInt() throws IOException {
        return Integer.parseInt(readString());
    }

    @SuppressWarnings("unused")
    private long readLong() throws IOException {
        return Long.parseLong(readString());
    }

    @SuppressWarnings("unused")
    private double readDouble() throws IOException {
        return Double.parseDouble(readString());
    }
}