#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;
}