#include <bits/stdc++.h>   using namespace std;   static const int INF = 0x3f3f3f3f;   static const long long INFL = 0x3f3f3f3f3f3f3f3fLL;   void solve4() {     string s;     cin >> s;     int c = 0;     int n = int((s).size());     for (char ch : s) {       c += (ch ==  a );     }     long long ans;     cerr <<  n           <<  =  << n <<  ,           <<  c           <<  =  << c << endl;     if (c > n / 2)       ans = n;     else       ans = 2 * c - 1;     cout << ans << endl;   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     solve4();   }   