#include<stdio.h>
int main()
{short N,i,c1=0,c2=0;char v[32000];
scanf("%i",&N);
for(i=0;i<N;i++)scanf("%i",v+i);
for(i=0;i<N;i++) if(v[i]%2==i%2)c1++;else c2++;
if(c1>c2)c1=c2;
printf("%i",c1);
return 0;
}