#include <bits/stdc++.h>
using namespace std;
const int maxn = 5000 + 10;
int n, sa[maxn], sb[maxn];
string s;
int kq;
int main() {
  cin >> s;
  n = s.length();
  sa[0] = sb[0] = 0;
  for (int i = 1; i <= n + 1; i++) {
    sa[i] = sa[i - 1];
    sb[i] = sb[i - 1];
    if (i <= n && s[i - 1] == 'a') sa[i]++;
    if (i <= n && s[i - 1] == 'b') sb[i]++;
  }
  for (int i = 0; i <= n + 1; i++)
    for (int j = i; j <= n + 1; j++)
      kq = max(kq, i - (sb[i]) + (j - i) - (sa[j] - sa[i]) + (n - j) -
                       (sb[n + 1] - sb[j]));
  printf("%d", kq);
}
