#include <bits/stdc++.h>
using namespace std;
int main() {
    string s;
    cin >> s;

    char old = s[0];

    long long count = 0;
    bool flag = false;

    long long temp_count = 1;

    for (int i = 1; i < s.size(); i++) {
        if (old == s[i]) {
            temp_count++;
        } else {
            count += temp_count / 3 * 2;
            int mod = temp_count % 3;

            if (mod > 0) {
                count++;
            } 

            if (! flag && mod == 2) {
                flag = trube;
            } else if (flag && mod == 2) {
                count++;
                flag = false;
            } else if (mod == 1) {
                flag = false;
            }

            temp_count = 1;
        }
        old = s[i];
    }

    count += temp_count / 3 * 2;
    int mod = temp_count % 3;
    if (mod > 0) {
        count++;
    }
    if (mod > 1) {
        if (flag) {
            count++;
        } 
    }

    cout << count;
}