#include <iostream>#include <stdio.h>using namespace std;int main(){ int a[10001],n,i,b[10001],min; while( cin>>n && n!=EOF ) { for(i=0;i<n;i++) { cin>>a[i]; b[i]=a[i]; } int sum1=0; for(i=1;i<n;i++) if(a[i]==a[i-1]) { a[i]=!a[i-1]; sum1++; } b[0]=!b[0]; int sum2=1; for(i=1;i<n;i++) if(b[i]==b[i-1]) { b[i]=!b[i-1]; sum2++; } min= sum1<sum2 ? sum1:sum2; cout<<min<<endl; } return 0;}


