Problem:
Score : 600 points

Problem Statement

Snuke stands on a number line. He has L ears, and he will walk along the line continuously under the following conditions:

He never visits a point with coordinate less than 0, or a point with coordinate greater than L.

He starts walking at a point with integer coordinate, and also finishes walking at a point with integer coordinate.

He only changes direction at a point with integer coordinate.

Each time when Snuke passes a point with coordinate i-0.5, where i is an integer, he put a stone in his i-th ear.

After Snuke finishes walking, Ringo will repeat the following operations in some order so that, for each i, Snuke's i-th ear contains A_i stones:

Put a stone in one of Snuke's ears.

Remove a stone from one of Snuke's ears.

Find the minimum number of operations required when Ringo can freely decide how Snuke walks.

Constraints

1 \leq L \leq 2\times 10^5

0 \leq A_i \leq 10^9(1\leq i\leq L)

All values in input are integers.

Input

Input is given from Standard Input in the following format:

L
A_1
:
A_L

Output

Print the minimum number of operations required when Ringo can freely decide how Snuke walks.

Sample Input 1

4
1
0
2
3

Sample Output 1

1

Assume that Snuke walks as follows:

He starts walking at coordinate 3 and finishes walking at coordinate 4, visiting coordinates 3,4,3,2,3,4 in this order.

Then, Snuke's four ears will contain 0,0,2,3 stones, respectively.
Ringo can satisfy the requirement by putting one stone in the first ear.

Sample Input 2

8
2
0
0
2
1
3
4
1

Sample Output 2

3

Sample Input 3

7
314159265
358979323
846264338
327950288
419716939
937510582
0

Sample Output 3

1

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.*;
import java.util.*;

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

    void solve() {
        int n = ni();
        long a[] = new long[n], sum = 0;
        for (int i = 0; i < n; ++i) {
            a[i] = nl();
            sum += a[i];
        }
        long b[] = new long[n + 1];
        long e[] = new long[n + 1];
        for (int i = 0; i < n; ++i) {
            b[i + 1] = a[i] - (a[i] % 2 == 0 ? 1 : 0);
            e[n - i] = a[i] - (a[i] % 2 == 0 ? 1 : 0);
        }
        for (int i = 0; i < n; ++i) {
            if (b[i] < 0) b[i] = 0;
            b[i + 1] += b[i];
            if (e[i] < 0) e[i] = 0;
            e[i + 1] += e[i];
        }
        long c[] = new long[n + 1];
        long d[] = new long[n + 1];
        for (int i = 0; i < n; ++i) {
            if (a[i] == 0) {
                c[i + 1] = -2;
                d[n - i] = -2;
            } else {
                c[i + 1] = a[i] - (a[i] % 2 == 1 ? 1 : 0);
                d[n - i] = a[i] - (a[i] % 2 == 1 ? 1 : 0);
            }
        }
        for (int i = 0; i < n; ++i) {
            if (c[i] < 0) c[i] = 0;
            c[i + 1] += c[i];
            if (d[i] < 0) d[i] = 0;
            d[i + 1] += d[i];
        }
        int r = 0, l = 0;
        long rv = 0, lv = 0;
        for (int i = 0; i <= n; ++i) {
            if (rv < c[i] - b[i]) {
                rv = c[i] - b[i];
                r = i;
            }
            if (lv < d[i] - e[i]) {
                lv = d[i] - e[i];
                l = i;
            }
        }
        long result = 0;
        if (r <= n - l) {
            result = Math.max(result, c[r] + d[l] + b[n - l] - b[r]);
        }
        for (int i = 0; i <= n; ++i) {
            result = Math.max(result, Math.max(c[i], b[i]) + Math.max(d[n - i], e[n - i]));
        }
        out.println(sum - result);
    }

    public static void main(String[] args) throws Exception {
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);
        new Main().solve();
        out.flush();
    }

    private static boolean eof() {
        if (lenbuf == -1) return true;
        int lptr = ptrbuf;
        while (lptr < lenbuf)
            if (!isSpaceChar(inbuf[lptr++])) return false;

        try {
            is.mark(1000);
            while (true) {
                int b = is.read();
                if (b == -1) {
                    is.reset();
                    return true;
                } else if (!isSpaceChar(b)) {
                    is.reset();
                    return false;
                }
            }
        } catch (IOException e) {
            return true;
        }
    }

    private static byte[] inbuf = new byte[1024];
    static int lenbuf = 0, ptrbuf = 0;

    private static 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 static boolean isSpaceChar(int c) {
        return !(c >= 33 && c <= 126);
    }

    private static int skip() {
        int b;
        while ((b = readByte()) != -1 && isSpaceChar(b))
            ;
        return b;
    }

    private static double nd() {
        return Double.parseDouble(ns());
    }

    private static char nc() {
        return (char) skip();
    }

    private static String ns() {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    private static 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 static 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 static int[] na(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = ni();
        return a;
    }

    private static long[] nal(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = ni();
        return a;
    }

    private static 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 static 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 class XorShift {
        int x = 123456789;
        int y = 362436069;
        int z = 521288629;
        int w = 88675123;

        int nextInt(int n) {
            final int t = x ^ (x << 11);
            x = y;
            y = z;
            z = w;
            w = (w ^ (w >>> 19)) ^ (t ^ (t >>> 8));
            final int r = w % n;
            return r < 0 ? r + n : r;
        }
    }

    private static void tr(Object... o) {
        System.err.println(Arrays.deepToString(o));
    }
}