#include <bits/stdc++.h>
using namespace std;
long long int ac[6000], bc[6000];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int n, sum = 0, count = 0, m, flag = 0, ans = 1e15, k;
  string a;
  cin >> a;
  a = "$" + a;
  n = a.length();
  for (int i = 1; i < n; i++) {
    if (a[i] == 'a')
      ac[i] = ac[i - 1] + 1;
    else
      ac[i] = ac[i - 1];
    if (a[i] == 'b')
      bc[i] = bc[i - 1] + 1;
    else
      bc[i] = bc[i - 1];
  }
  ac[n] = ac[n - 1];
  bc[n] = bc[n - 1];
  for (int i = 0; i <= n; i++) {
    for (int j = i; j <= n; j++) {
      if (i == j) {
        ans = min(ans, bc[i] + bc[n] - bc[j - 1]);
      } else
        ans = min(ans, bc[i] + bc[n] - bc[j - 1] + ac[j - 1] - ac[i]);
    }
  }
  cout << n - ans - 1 << endl;
  return 0;
}
