#include <bits/stdc++.h>
using namespace std;
int binarySearch(int arr[], int l, int r, int x) {
  while (l <= r) {
    int m = l + (r - l) / 2;
    if (arr[m] == x) return m;
    if (arr[m] < x)
      l = m + 1;
    else
      r = m - 1;
  }
  return -1;
}
bool isprime(int n) {
  if (n <= 1) return false;
  for (int i = 2; i < n; i++)
    if (n % i == 0) return false;
  return true;
}
long long int factorial(int n) {
  if (n == 0) return 1;
  return n * factorial(n - 1);
}
int countDigit(long long n) {
  int count = 0;
  while (n != 0) {
    n = n / 10;
    ++count;
  }
  return count;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  int counta[s.length()], countb[s.length()],
      dp[s.length() + 1][s.length() + 1], mini = 1000000;
  counta[0] = countb[0] = 0;
  for (int i = 0; i < s.length(); i++) {
    if (i == 0) {
      if (s[i] == 'a')
        counta[0]++;
      else
        countb[0]++;
    } else {
      if (s[i] == 'a') {
        counta[i] = counta[i - 1] + 1;
        countb[i] = countb[i - 1];
      } else {
        counta[i] = counta[i - 1];
        countb[i] = countb[i - 1] + 1;
      }
    }
  }
  for (int i = 0; i <= s.length(); i++) {
    for (int j = i; j <= s.length(); j++) {
      if (j > 0 && i > 0)
        dp[i][j] = countb[i - 1] + (counta[j - 1] - counta[i - 1]) +
                   countb[s.length() - 1] - countb[j - 1];
      if (i == 0 && j > 0)
        dp[i][j] = (counta[j - 1]) + countb[s.length() - 1] - countb[j - 1];
      if (i == 0 && j == 0) dp[i][j] = countb[s.length() - 1];
    }
  }
  for (int i = 0; i <= s.length(); i++) {
    for (int j = i; j <= s.length(); j++) mini = min(mini, dp[i][j]);
  }
  cout << s.length() - mini;
  return 0;
}
