#include <bits/stdc++.h>
using namespace std;
int main() {
  string second;
  int dp1[5001], dp2[5001], a, pre, i;
  pre = -1;
  a = 0;
  cin >> second;
  for (i = 0; i < second.length(); i++) {
    if (second[i] == 'a')
      a++;
    else {
      if (pre == -1)
        dp1[i] = a + 1;
      else
        dp1[i] = max(dp1[pre], a) + 1;
      pre = i;
    }
  }
  int xam = a;
  pre = -1;
  a = 0;
  for (i = second.length() - 1; i >= 0; i--) {
    if (second[i] == 'a')
      a++;
    else {
      if (pre == -1)
        dp2[i] = a;
      else
        dp2[i] = max(dp2[pre], a);
      pre = i;
      xam = max(xam, dp1[i] + dp2[i]);
    }
  }
  cout << xam;
  return 0;
}
