#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const long long INF = 1e10;
template <typename T>
void cmax(T &a, T b) {
  a = max(a, b);
}
template <typename T>
void cmin(T &a, T b) {
  a = min(a, b);
}
signed main() {
  string s;
  cin >> s;
  long long a[5555] = {};
  long long b[5555] = {};
  for (long long i = 0; i < (s.size()); i++) {
    a[i + 1] += a[i];
    b[i + 1] += b[i];
    if (s[i] == 'a')
      a[i + 1]++;
    else
      b[i + 1]++;
  }
  long long ans = 0;
  for (long long i = 0; i < (s.size() + 1); i++)
    for (long long j = (i); j < (s.size() + 1); j++)
      cmax(ans, a[s.size()] - a[j] + b[j] - b[i] + a[i]);
  cout << ans << endl;
  return 0;
}
