#include <bits/stdc++.h>
using namespace std;
int dp[5001][3];
char str[5002];
int N;
int solve(int idx, int flag) {
  if (idx == N) return 0;
  int &ret = dp[idx][flag];
  if (ret != -1) return ret;
  ret = -987654321;
  if (flag == 0) {
    ret = max(ret, solve(idx + 1, 0) + (str[idx] == 'a' ? 1 : 0));
    ret = max(ret, solve(idx + 1, 1) + (str[idx] == 'a' ? 1 : 0));
  } else if (flag == 1) {
    ret = max(ret, solve(idx + 1, 1) + (str[idx] == 'b' ? 1 : 0));
    ret = max(ret, solve(idx + 1, 2) + (str[idx] == 'b' ? 1 : 0));
  } else {
    ret = max(ret, solve(idx + 1, 2) + (str[idx] == 'a' ? 1 : 0));
  }
  return ret;
}
int main() {
  memset(dp, -1, sizeof dp);
  scanf("%s", &str);
  N = strlen(str);
  printf("%d\n", max(solve(0, 1), max(solve(0, 2), solve(0, 0))));
  return 0;
}
