#include <bits/stdc++.h>
using namespace std;
long long modx(long long Base, long long exponent) {
  long long ans = 1;
  if (Base == 1) return Base;
  while (exponent) {
    if (exponent & 1) ans = (ans * Base) % 1000000007LL;
    Base = (Base * Base) % 1000000007LL;
    exponent = exponent >> 1;
  }
  return ans;
}
long long inmodx(long long num) { return (modx(num, 1000000007LL - 2LL)); }
bool cmp(pair<pair<int, int>, int> a, pair<pair<int, int>, int> b) {
  if (a.first.first / 900 < b.first.first / 900) return 1;
  if (a.first.first / 900 > b.first.first / 900) return 0;
  if (a.first.second <= b.first.second) return 1;
  return 0;
}
const int N = (5e3) + 9;
const int M = (N << 2) + 9;
const int LOGN = ((int)log2(N)) + 3;
const int LOGM = ((int)log2(M)) + 3;
const int BUCK = 450;
string s;
int a[N], b[N];
int calc(int x[], int l, int r) {
  if (l > r) return 0;
  return (x[r] - x[l - 1]);
}
void solve() {
  int n, i, j, ans = 0, val;
  cin >> s;
  n = s.length();
  for (i = (0); i < (n); i++) {
    a[i + 1] = a[i];
    b[i + 1] = b[i];
    if (s[i] == 'a')
      a[i + 1]++;
    else
      b[i + 1]++;
  }
  ans = max(a[n], b[n]);
  for (i = (1); i < (n + 1); i++)
    for (j = (i); j < (n + 1); j++) {
      val = calc(a, 1, i - 1) + calc(b, i, j) + calc(a, j + 1, n);
      ans = max(ans, val);
    }
  cout << ans << '\n';
  return;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1, cs;
  cout << fixed << setprecision(9);
  for (cs = (1); cs < (t + 1); cs++) {
    solve();
  }
  return 0;
}
