#include <bits/stdc++.h>
bool debug = 1;
const double PI = acos(-1.0);
const double eps = 1e-9;
using namespace std;
int a;
int pref[100100];
int suf[100100];
int main() {
  string s;
  cin >> s;
  int n = s.size();
  pref[0] = 0;
  for (int i = 0; i < n; i++) {
    pref[i + 1] = pref[i];
    if (s[i] == 'a') {
      a++;
      pref[i + 1] += 1;
    }
  }
  suf[0] = 0;
  for (int i = n - 1; i >= 0; i--) {
    suf[n - i] = suf[n - i - 1];
    if (s[i] == 'a') {
      suf[n - i]++;
    }
  }
  int res = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; i + j <= n; j++) {
      res = max(pref[i] + suf[j] + n - i - j - (a - pref[i] - suf[j]), res);
    }
  }
  cout << res << endl;
  return 0;
}
