#include <bits/stdc++.h>
using namespace std;
const int maxn = 5e3 + 500;
int befa[maxn], befb[maxn], afta[maxn], aftb[maxn];
string s;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> s;
  int n = s.size();
  if (n == 1) {
    cout << 1 << endl;
    return 0;
  }
  int ans = 1000000000;
  if (s[0] == 'a') befa[0] = 1;
  for (int i = 1; i < n; i++) {
    if (s[i] == 'a')
      befa[i] = befa[i - 1] + 1;
    else
      befa[i] = befa[i - 1];
  }
  if (s[n - 1] == 'a') afta[n - 1] = 1;
  for (int i = n - 2; i >= 0; i--) {
    if (s[i] == 'a')
      afta[i] = afta[i + 1] + 1;
    else
      afta[i] = afta[i + 1];
  }
  if (s[0] == 'b') befb[0] = 1;
  for (int i = 1; i < n; i++) {
    if (s[i] == 'b')
      befb[i] = befb[i - 1] + 1;
    else
      befb[i] = befb[i - 1];
  }
  if (s[n - 1] == 'b') aftb[n - 1] = 1;
  for (int i = n - 2; i >= 0; i--) {
    if (s[i] == 'b')
      aftb[i] = aftb[i + 1] + 1;
    else
      aftb[i] = aftb[i + 1];
  }
  for (int i = 0; i < n; i++) {
    for (int j = i; j < n; j++) {
      bool cur = false, bak = false, bok = false;
      if (s[i] == 'a' && i != j) cur = true;
      if (s[j] == 'b') bak = true;
      if (s[i] == 'b') bok = true;
      int k = aftb[j] - bak + befb[i] - bok + (befa[j] - befa[i] + cur);
      ans = min(k, ans);
    }
  }
  cout << n - ans << endl;
}
