#include <bits/stdc++.h>
using namespace std;
int accA[5005], accB[5005];
string s;
int res = 0;
int main() {
  string s;
  while (cin >> s) {
    accA[0] = accB[0] = 0;
    for (int i = 0; i < s.size(); i++) {
      if (s[i] == 'a')
        accA[i + 1] = accA[i] + 1;
      else
        accA[i + 1] = accA[i];
      if (s[i] == 'b')
        accB[i + 1] = accB[i] + 1;
      else
        accB[i + 1] = accB[i];
    }
    int n = s.size();
    int res = max(accB[n], accA[n]);
    for (int i = 1; i <= n; i++) {
      for (int j = i; j <= n; j++) {
        res = max(res, accA[max(i - 1, 0)] - accA[0] + accA[n] - accA[j] +
                           accB[j] - accB[i - 1]);
      }
    }
    cout << res << endl;
  }
  return 0;
}
