#include <bits/stdc++.h>
using namespace std;
string s;
long long dpa[5005], dpb[5005], ans;
void solve() {
  cin >> s;
  for (__typeof(((long long)s.size())) i = (0); i < ((long long)s.size());
       i++) {
    dpa[i + 1] = dpa[i] + (s[i] == 'a');
    dpb[i + 1] = dpb[i] + (s[i] == 'b');
  }
  ans = max(dpa[(long long)s.size()], dpb[(long long)s.size()]);
  for (__typeof(((long long)s.size() + 1)) i = (1);
       i < ((long long)s.size() + 1); i++) {
    for (__typeof(((long long)s.size() + 1)) j = (i);
         j < ((long long)s.size() + 1); j++)
      ans = max(ans, dpa[i - 1] + dpb[j] - dpb[i - 1] +
                         dpa[(long long)s.size()] - dpa[j - 1]);
  }
  {
    cout << ans << "\n";
    return;
  };
}
void prep() {}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  prep();
  cout << fixed << setprecision(12);
  while (t--) solve();
  return 0;
}
