#include <iostream>
using namespace std;
#define MAXLENGTH 10000
int main() {
    int N{ 0 }, n{ 0 };
    char per[4] = "PER";
    char* cstr = new char[MAXLENGTH];
    cin.getline(cstr, MAXLENGTH);
    n = strlen(cstr);
    for (int i = 0; i < n; ++i, ++cstr)
        if (*cstr != per[i % 3]) 
            ++N;
    cout << N;
}