#include <iostream>
#include <iterator>
using namespace std;

int main() {
   string s;
   cin >> s;
   for(char &c :s){
    if(c>='A' && c<='Z'){
        c+=32;
    }
   }
   size_t pos = s.find("bob");
   if(pos!=string::npos){
    cout << pos <<endl;
   }else{
    cout << -1 <<endl;
   }
}

string的find函数