C. Garland

#include <iostream>
#include <string>
#include <string.h>
#include <stdio.h>
#include <algorithm>
#include <map>
 
using namespace std;
 
const int N = 101;
int a[N];
int dp[N][N][N][2];
int n;
int dfs(int k, int h, int w, int z)
{
    if (dp[k][h][w][z] != -1)
    {
        return dp[k][h][w][z];
    }
    if (k == 0)
    {
        if ((z == 1 && (a[k] == 0 || a[k]&0x01)) && h > 0)
        return (dp[k][h][w][z] = 0);
        if ((z == 0 && (a[k] == 0 || !(a[k]&0x01))) && w > 0)
            return (dp[k][h][w][z] = 0);
        return (dp[k][h][w][z] = N);
    }
    dp[k][h][w][z] = N;
    if(a[k] == 0)
    {
        if (z == 1 && h > 0)
        {
            if (h > 1)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h-1, w, 1));
            }
            if (w > 0)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h-1, w, 0) + 1);
            }
 
        }
        if (z == 0 && w > 0)
        {
            if (w > 1)
            {
                 dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h, w-1, 0));
            }
            if (h > 0)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h, w-1, 1) + 1);
            }
        }
    }
    else if(a[k]&0x01)
    {
        if (z == 1 && h > 0)
        {
            if (h > 1)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h-1, w, 1));
            }
            if (w > 0)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h-1, w, 0) + 1);
            }
 
        }
    }
    else
    {
        if (z == 0 && w > 0)
        {
            if (w > 1)
            {
                 dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h, w-1, 0));
            }
            if (h > 0)
            {
                dp[k][h][w][z] = min(dp[k][h][w][z], dfs(k-1, h, w-1, 1) + 1);
            }
        }
    }
    //cout << k <<" " <<h << " " << w << " " << z << " " << dp[k][h][w][z] << endl;
    return dp[k][h][w][z];
}
 
int main()
{
    while(cin>>n)
    {
        for (int i = 0; i < n; ++i)
        {
            cin>>a[i];
        }
        if (n == 1)
        {
            cout << 0 << endl;
            continue;
        }
        if (n == 2)
        {
            cout << 1 << endl;
            continue;
        }
 
        memset(dp, -1, sizeof(dp));
 
        int h = n >> 1;
        if (n&0x01)
        {
            h ++;
        }
 
        cout << min(dfs(n-1, h, n-h, 1), dfs(n-1, h, n-h, 0)) << endl;
    }
    return 0;
}