#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  vector<int> a(s.size() + 1, 0), b(s.size() + 1, 0);
  for (int i = 1; i <= int(s.size()); i++) {
    a[i] += (s[i - 1] == 'a') + a[i - 1];
    b[i] += (s[i - 1] == 'b') + b[i - 1];
  }
  int ans = 0;
  for (int i = 0; i < int(s.size()); i++)
    for (int j = i; j <= int(s.size()); j++)
      ans = max(ans, int(s.size()) - b[i] - (a[j] - a[i]) -
                         (b[int(s.size())] - b[j]));
  cout << ans;
  return 0;
}
