#include <bits/stdc++.h>
using namespace std;
int n,a[1001];
int has[1001];
int dp[101][101][101];
int cal(int i){
if(i==0)return 0;
return (a[i-1]%2)!=(a[i]%2);
}
int fun(int i,int e,int o){
if(i==n){
return 0;
}
//cout<<"hello\n";
if(dp[i][e][o]!=-1)return dp[i][e][o];
else if(a[i]==0){
int x,y;
if(e>=1){
a[i]=2;
x=cal(i)+fun(i+1,e-1,o);
a[i]=0;
}
else{
x=1000;
}
if(o>=1){
a[i]=1;
y=cal(i)+fun(i+1,e,o-1);
a[i]=0;
}
else{
y=1000;
}
return dp[i][e][o]=min(x,y);
}
else{
return dp[i][e][o]=cal(i)+fun(i+1,e,o);
}
}
int main() {
cin>>n;
int even=0,odd=0;
for(int i=0;i<n;i++){
cin>>a[i];
has[a[i]]++;
}
for(int i=1;i<=n;i++){
if(has[i]==0){
if(i%2==1){
odd++;
}
else{
even++;
}
// cout<<i<<endl;
}
}
for(int i=0;i<=n;i++){
for(int j=0;j<=even;j++){
for(int k=0;k<=odd;k++){
dp[i][j][k]=-1;
}
}
}
cout<<fun(0,even,odd)<<endl;
return 0;
}
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