#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int i, j, cntb = 0, totb = 0, sum = 1e6, cnt;
  cin >> s;
  int a[5005];
  if (s[0] == 'a')
    a[0] = 1;
  else
    a[0] = 0, totb++;
  for (i = 1; s[i]; i++) {
    if (s[i] == 'a')
      a[i] = a[i - 1] + 1;
    else
      a[i] = a[i - 1], totb++;
  }
  for (i = 0; s[i]; i++) {
    if (s[i] == 'b') {
      int cnt = 0;
      for (j = i; s[j]; j++) {
        if (s[j] == 'b') {
          cnt++;
          sum = min(sum, a[j] - a[i] + totb - cnt);
        }
      }
    }
  }
  if (sum == 1e6)
    cout << s.size();
  else
    cout << s.size() - sum;
  return 0;
}
