#include <bits/stdc++.h>
using namespace std;
signed main() {
  string s;
  vector<pair<long long, long long> > data;
  cin >> s;
  data.push_back(make_pair(0, 0));
  for (long long i = 1; i <= s.size(); i++) {
    if (s[i - 1] == 'a') {
      data.push_back(make_pair(data[i - 1].first + 1, data[i - 1].second));
    } else {
      data.push_back(make_pair(data[i - 1].first, data[i - 1].second + 1));
    }
  }
  long long ans = 0;
  for (long long i = 0; i <= s.size(); i++) {
    for (long long j = 0; j <= s.size(); j++) {
      long long l, r;
      l = min(i, j);
      r = max(i, j);
      ans = max(ans, data[l].first + data[r].second - data[l].second +
                         data[s.size()].first - data[r].first);
    }
  }
  cout << ans << endl;
  return 0;
}
