#include <bits/stdc++.h>
using namespace std;
long long dp[5002][3], mx, mx1, mx2, ans;
int32_t main() {
  ios::sync_with_stdio(0), cin.tie(0);
  string s;
  cin >> s;
  for (long long i = 0; i < s.size(); ++i) {
    if (i) {
      dp[i][0] = dp[i - 1][0] + (long long)(s[i] == 'a');
      dp[i][1] = max(dp[i - 1][1], dp[i][0]) + (long long)(s[i] == 'b');
      dp[i][2] = max(dp[i - 1][2] + (long long)(s[i] == 'a'), dp[i][1]);
    } else {
      dp[0][0] = (long long)(s[0] == 'a');
      dp[0][1] =
          max(dp[0][0] + (long long)(s[0] == 'b'), (long long)(s[0] == 'b'));
      dp[i][2] = max((long long)(s[0] == 'a'), dp[i][1]);
    }
    ans = max(ans, max(dp[i][0], max(dp[i][1], dp[i][2])));
  }
  cout << ans << '\n';
}
