#include <bits/stdc++.h>
using namespace std;
int n, i, j, k, l, m, v, dp[3][5050];
vector<string> q;
string s, s1;
int main() {
  cin >> s;
  for (i = 0; i < s.size(); i++) {
    dp[0][i + 1] = dp[0][i] + (s[i] == 'a');
    dp[1][i + 1] = max(dp[0][i], dp[1][i]) + (s[i] == 'b');
    dp[2][i + 1] = max(dp[2][i], dp[1][i]) + (s[i] == 'a');
  }
  cout << max(dp[0][s.size()], max(dp[1][s.size()], dp[2][s.size()]));
}
