#include <bits/stdc++.h>
using namespace std;
char str[5005];
int l[5005];
int r[5005];
int main() {
  while (scanf("%s", str) == 1) {
    int len = strlen(str);
    l[0] = 0;
    r[len + 1] = 0;
    for (int i = 0; i < len; i++)
      if (str[i] == 'a')
        l[i + 1] = l[i] + 1;
      else
        l[i + 1] = l[i];
    for (int i = len - 1; i >= 0; i--)
      if (str[i] == 'a')
        r[i + 1] = r[i + 2] + 1;
      else
        r[i + 1] = r[i + 2];
    int ans = 0;
    for (int i = 1; i <= len; i++) {
      ans = max(ans, l[i] + len - i - r[i + 1]);
      ans = max(ans, i - l[i] + r[i + 1]);
    }
    for (int i = 1; i <= len; i++)
      for (int j = i + 1; j <= len; j++) {
        ans = max(ans, l[i] + r[j] + j - i - 1 - l[j - 1] + l[i]);
      }
    printf("%d\n", ans);
  }
  return 0;
}
