#include <bits/stdc++.h>
using namespace std;
const int N = 5005;
char s[N];
int prefa[N], prefb[N];
int main() {
  cin >> (s + 1);
  int n = strlen(s + 1);
  int ans = -1;
  for (int i = 1; i <= n; i++) {
    if (s[i] == 'a') {
      prefa[i] = prefa[i - 1] + 1;
      prefb[i] = prefb[i - 1];
    } else {
      prefb[i] = prefb[i - 1] + 1;
      prefa[i] = prefa[i - 1];
    }
  }
  if (prefa[n] == n) {
    printf("%d\n", n);
    return 0;
  }
  for (int i = 1; i <= n; i++) {
    for (int j = i; j <= n; j++) {
      int temp =
          (prefa[n] - prefa[j]) + (prefb[j] - prefb[i - 1]) + (prefa[i - 1]);
      if (ans < temp) {
        ans = temp;
      }
    }
  }
  printf("%d\n", ans);
  return 0;
}
