#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int prefixa[5001], suffixa[5001], prefixb[5000];
  memset(prefixa, 0, sizeof(prefixa));
  memset(prefixb, 0, sizeof(prefixb));
  memset(suffixa, 0, sizeof(suffixa));
  if (s[0] == 'a')
    prefixa[0] = 1;
  else
    prefixb[0] = 1;
  for (int i = 1; i < s.length(); i++) {
    prefixa[i] = prefixa[i - 1];
    prefixb[i] = prefixb[i - 1];
    if (s[i] == 'a')
      prefixa[i]++;
    else
      prefixb[i]++;
  }
  if (s[s.length() - 1] == 'a') suffixa[s.length() - 1] = 1;
  for (int i = s.length() - 2; i >= 0; i--) {
    suffixa[i] = suffixa[i + 1];
    if (s[i] == 'a') suffixa[i]++;
  }
  int ans;
  for (int j = 0; j < s.length(); j++)
    ans = max(ans, prefixb[j] + suffixa[j + 1]);
  for (int i = 0; i < s.length(); i++)
    for (int j = i; j < s.length(); j++)
      ans = max(ans, prefixa[i] + prefixb[j] - prefixb[i] + suffixa[j + 1]);
  cout << ans << endl;
  return 0;
}
