#include<iostream> using namespace std; int n,a[40000],ans; signed main(){ cin>>n; int two=0,one=0; for(int i=1;i<=n;i++){ cin>>a[i]; if(a[i]==1){ one++; if(two&&one>two){ ans+=two; two=0; one=0; } }else if(a[i]==2){ if(two==0){ one=0; } two++; } } if(two)ans+=one; cout<<ans; return 0; }