#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ii pair <int,int>
#define F first
#define S second
#define ever (;;)

bool p0,p1;
int n,ans;

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        int x;
        scanf("%d",&x);

        if( x )
            p1 = 1;
        else
            p0 = 1;

        if( p1 && p0 )
        {
            p1 = p0 = 0;
            ans++;
        }
    }

    printf("%d\n",ans);
}