#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
#define CRP(t, x) const t &x
#define OPX(op, t, x) operator op(CRP(t, x))
#define OPL(t, x) bool OPX(<, t, x) const
#define FIL(x, v) memset(x, v, sizeof(x))
#define CLR(x) FIL(x, 0)
#define NE1(x) FIL(x, -1)
#define INF(x) FIL(x, 0x3f)
#ifndef _DEBUG
#define _DEBUG 0
#endif // !_DEBUG
#define IFD if (_DEBUG)
typedef int64_t ll, i64;
typedef uint64_t ull, u64;
template <typename... Types>
using comtype = typename common_type<Types...>::type;
template <typename T>
using enable_if_arithmetic = typename enable_if<is_arithmetic<T>::value>::type;
template <typename T>
using enable_if_integral = typename enable_if<is_integral<T>::value>::type;
inline char getchar(int)
{
    static char buf[64 << 20], *S = buf, *T = buf;
    if (S == T) T = fread(S = buf, 1, 64 << 20, stdin) + buf;
    return S == T ? EOF : *S++;
}
template <typename T, typename = enable_if_integral<T>>
inline bool read(T &x)
{
    int ch = x = 0, f = 1;
    while (!isdigit(ch = getchar()))
        if (ch == EOF)
            return false;
        else if (ch == '-')
            f = 0;
    for (; isdigit(ch); ch = getchar()) x = x * 10 + ch - '0';
    return x = f ? x : -x, true;
}
template <typename T, typename... Args, typename = enable_if_integral<T>>
inline bool read(T &x, Args &... args) { return read(x) && read(args...); }
template <typename T1, typename T2, typename TResult = comtype<T1, T2>>
inline TResult mmin(CRP(T1, v1), CRP(T2, v2)) { return min<TResult>(v1, v2); }
template <typename T, typename... Args, typename TResult = comtype<T, Args...>>
inline TResult mmin(CRP(T, v), const Args &... args) { return min<TResult>(v, mmin(args...)); }
template <typename T1, typename T2, typename TResult = comtype<T1, T2>>
inline TResult mmax(CRP(T1, v1), CRP(T2, v2)) { return max<TResult>(v1, v2); }
template <typename T, typename... Args, typename TResult = comtype<T, Args...>>
inline TResult mmax(CRP(T, v), const Args &... args) { return max<TResult>(v, mmax(args...)); }
inline ll gcd(ll a, ll b)
{
    for (; b; swap(a, b)) a %= b;
    return a;
}
inline ll fpow(ll a, ll b, ll m)
{
    ll r = 1;
    for (; b; b >>= 1, a = a * a % m)
        if (b & 1) r = r * a % m;
    return r;
}
constexpr double eps = 1e-8;
inline int sgn(double x) { return x > eps ? 1 : x < -eps ? -1 : 0; }
int a[105];
int main()
{
    int n;
    read(n);
    for (int i = 0; i < n; i++) read(a[i]);
    int c[2];
    c[0] = n >> 1, c[1] = n - c[0];
    vector<pair<int, int>> zseg, bseg;
    for (int i = 0; i < n;)
        if (a[i] == 0)
        {
            int j = i;
            while (j < n && a[j] == 0) j++;
            zseg.push_back({i, j});
            i = j;
        }
        else
            c[a[i++] & 1]--;
    int ans = 0;
    for (int i = 1; i < n; i++)
        if (a[i - 1] && a[i] && ((a[i - 1] ^ a[i]) & 1)) ans++;
    if (zseg.size() == 0) return printf("%d", ans), 0;
    if (zseg.size() == 1 && zseg.front().first == 0 && zseg.front().second == n)
        return puts(n == 1 ? "0" : "1"), 0;
    for (CRP(auto, seg) : zseg)
        if (seg.first != 0 && seg.second != n)
            if ((a[seg.first - 1] ^ a[seg.second]) & 1 ^ 1)
                bseg.push_back(seg);
            else
                ans++;
    sort(bseg.begin(), bseg.end(), [](CRP(auto, l), CRP(auto, r)) { return l.second - l.first < r.second - r.first; });
    for (CRP(auto, seg) : bseg)
    {
        if (c[a[seg.second] & 1] >= seg.second - seg.first)
            c[a[seg.second] & 1] -= seg.second - seg.first;
        else
            ans += 2;
    }
    CRP(auto, fr) = *zseg.begin();
    if (fr.first == 0)
        if (c[a[fr.second] & 1] >= fr.second - fr.first)
            c[a[fr.second] & 1] -= fr.second - fr.first;
        else
            ans++;
    CRP(auto, la) = *zseg.rbegin();
    if (la.second == n)
        if (c[a[la.first - 1] & 1] >= la.second - la.first)
            c[a[la.first - 1] & 1] -= la.second - la.first;
        else
            ans++;
    printf("%d", ans);
    return 0;
}