#include <bits/stdc++.h>
int max(int a, int b) {
  if (a > b) return a;
  return b;
}
int main() {
  char a[5005];
  scanf("%s", a);
  int n = strlen(a), i, j;
  int count[5005][2];
  if (a[0] == 'a')
    count[0][0] = 1, count[0][1] = 1;
  else
    count[0][1] = 1, count[0][0] = 0;
  for (i = 1; i < n; i++)
    if (a[i] == 'a') {
      count[i][0] = count[i - 1][0] + 1;
      count[i][1] = count[i - 1][1];
    } else {
      count[i][1] = count[i - 1][1] + 1;
      count[i][0] = count[i - 1][0];
    }
  int ans = 0, max = 0;
  for (i = 0; i < n; i++) {
    ans = 0;
    for (j = i; j < n; j++) {
      ans = 0;
      ans += (count[i][0]) + (count[j][1] - count[i][1]) +
             (count[n - 1][0] - count[j][0]);
      if (a[i] == 'b') ans++;
      if (ans > max) max = ans;
    }
  }
  printf("%d\n", max);
  return 0;
}
