#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 1e6 + 10;

char str[N];
bool st[N];

int main() {
    cin >> str + 1;
    int ans = 0;
    for (int i = 2; str[i]; i ++ ) {
        if (st[i - 1]) continue;
        if ((str[i] == str[i - 1]) || (str[i] == '?') || (str[i - 1] == '?')) {
            ans ++ ;
            st[i] = true;
        }
    }

    cout << ans;

    return 0;
}