#include<iostream>
#include<vector>
using namespace std;
string s;
main()
{
	cin>>s;
	s+="00";
	vector<int>T;
	int cnt=1;
	for(int i=1;i<s.size();i++)
	{
		if(s[i-1]!=s[i])
		{
			T.push_back(cnt);
			cnt=1;
		}
		else cnt++;
	}
	T.push_back(cnt);
	int ans=0;
	for(int i=0;i<T.size();i+=2)
	{
		int cnt=0;
		bool flag=T[i]>1;
		while(i+2<T.size()&&T[i+1]==1)
		{
			cnt++;
			i+=2;
			flag|=T[i]>1;
		}
		ans+=flag?cnt+2:cnt+1;
	}
	cout<<ans<<endl;
}