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

#define all(x) begin(x), end(x)

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);

    string in;
    cin >> in;

    int ans = 0;

    for (int i = 1; i < in.size(); ++i) {
        if (in[i] == in[i-1]) ans++;
    }

    ans++;
    ans /= 2;


    cout << ans << endl;



	return 0;
			
}