#include <bits/stdc++.h>
using namespace std;
const int N = 5e3 + 7;
int cnt1[N];
int cnt2[N];
int cnt3[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  int n = s.size();
  memset(cnt1, 0, sizeof(cnt1));
  memset(cnt2, 0, sizeof(cnt2));
  memset(cnt3, 0, sizeof(cnt3));
  for (int i = 1; i <= n; i++) {
    cnt1[i] = cnt1[i - 1], cnt3[i] = cnt3[i - 1];
    cnt1[i] += (s[i - 1] != 'a');
    cnt3[i] += (s[i - 1] != 'b');
  }
  for (int i = n; i >= 1; i--) {
    cnt2[i] = cnt2[i + 1];
    cnt2[i] += (s[i - 1] != 'a');
  }
  int ans = min(cnt1[n], cnt3[n]);
  for (int i = 1; i <= n; i++) {
    for (int j = n; j > i; j--) {
      ans = min(ans, cnt1[i] + cnt2[j] + cnt3[j - 1] - cnt3[i]);
    }
  }
  for (int i = 0; i <= n; i++) {
    ans = min(ans, cnt1[i] + cnt2[i + 1]);
    ans = min(ans, cnt1[i] + cnt3[n] - cnt3[i]);
    ans = min(ans, cnt3[i] + cnt2[i + 1]);
  }
  cout << (n - ans) << endl;
  return 0;
}
