#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e9;
const long long MOD = 1e9 + 7;
const long long N = 1e5;
long long a[100005];
void solve() {
  string s;
  cin >> s;
  string t = "";
  long long ans = 0;
  long long n = s.size();
  vector<long long> pref(n + 1);
  vector<long long> pf(n + 1);
  for (long long i = 0; i < n; i++) {
    pref[i + 1] = pref[i] + (s[i] == 'a');
  }
  for (long long i = 0; i < n; i++) {
    pf[i + 1] = pf[i] + (s[i] == 'b');
  }
  for (long long l = 0; l <= n; l++) {
    for (long long r = l; r <= n; r++) {
      long long cnt1 = pref[l];
      long long cnt2 = pref[n] - pref[r];
      long long cnt3 = pf[r] - pf[l];
      ans = max(cnt1 + cnt2 + cnt3, ans);
    }
  }
  cout << ans << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long t = 1;
  while (t--) solve();
  return 0;
}
