#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
#include <cmath>
#include <iomanip>
#include <map>
#include <set>
#include <bitset>

using namespace std;

int main()
{
	ios_base::sync_with_stdio(0);

	int res = 0;
	char last = 'A';
	char c1, c2;

	while (cin >> c1 >> c2)
	{
		if (last == 'A') 
		{
			last = c2;
		}
	
		if (last == c1)
			res++;

		last = c2;
	}

	cout << (res + 1) / 2 << endl;

	return 0;
}