#include<bits/stdc++.h>  
using namespace std;
int a[30005],b[30005];  
int n,m,ans,xb;
int main()
{      
    freopen("diningb.in", "r", stdin);
    freopen("diningb.out", "w", stdout);
    xb=300005;
    ans=xb;
    cin>>n;      
	for (int i=1;i<=n;i++) 
	cin>>a[i];     
	for (int i=1;i<=n;i++)          
	if (a[i]==2)
	    b[i]=++m;
	    else b[i]=m;      
	m=0;      
	for (int i=n;i>0;i--)
        if (a[i]==1) 
		b[i]+=++m;
		else b[i]+=m;           
	for (int i=1;i<=n;i++)          
	if (b[i]<ans) 
	ans=b[i];      
	cout<<ans-1<<endl;
	return 0;  
}