#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e5+1000;
typedef long long LL;
LL a[maxn];
LL sum0[maxn],sum1[maxn];
LL ones=0,zeros=0;
int main(void)
{
cin.tie(0);std::ios::sync_with_stdio(false);
LL n;cin>>n;
for(LL i=1;i<=n;i++){
cin>>a[i];
sum0[i]=sum0[i-1];sum1[i]=sum1[i-1];
if(a[i]) sum1[i]++,ones++;
else sum0[i]++,zeros++;
}
LL p=0x3f3f3f3f;
p=min(p,ones);
p=min(p,zeros+1);
for(LL i=1;i<=n;i++){
//到i这个位置的对前面0的操作,对后面的数进行单点
p=min(p,sum0[i]+1+ones-sum1[i]);
}
LL k=0;
for(LL i=1;i<=n;i++){
if(a[i]!=a[i+1]&&i+1!=n+1) k++;
}
if(a[n]==1) k++;
cout<<max(min(p,k),(LL)0)<<endl;
return 0;
}