#include <bits/stdc++.h>
using namespace std;
int fa[5010], ba[5010], b[5010];
int main() {
  ios_base::sync_with_stdio(0);
  int i, j, k, l, n, m, t, tt, x = 0, y;
  string s, second;
  cin >> s;
  n = s.length();
  fa[0] = 0;
  ba[n + 1] = 0;
  b[0] = 0;
  for (j = 1; j <= n; j++) {
    fa[j] = fa[j - 1];
    b[j] = b[j - 1];
    if (s[j - 1] == 'a')
      fa[j] = fa[j] + 1;
    else
      b[j] = b[j] + 1;
  }
  if (fa[n] == n) {
    cout << n << "\n";
    return 0;
  }
  for (j = n; j > 0; j--) {
    ba[j] = ba[j + 1];
    if (s[j - 1] == 'a') ba[j] = ba[j] + 1;
  }
  int mx = 0;
  for (i = 1; i <= n; i++) {
    for (j = i; j <= n; j++) {
      mx = max(fa[i - 1] + b[j] - b[i - 1] + ba[j + 1], mx);
    }
  }
  cout << mx;
  return 0;
}
