#include <bits/stdc++.h>
using namespace std;
int dp[5005][15], oo = 1e5;
char str[5005];
int solve(int i, int s) {
  if (str[i] == 0 and s == 2) {
    return 0;
  } else if (str[i] == 0 and s != 2) {
    return oo;
  } else if (~dp[i][s]) {
    return dp[i][s];
  } else {
    int ans = 0;
    if (s == 0) {
      if (str[i] == 'a') {
        ans = min(solve(i + 1, s), solve(i + 1, 1));
      } else {
        ans = min(solve(i + 1, s) + 1, solve(i + 1, 1));
      }
    } else if (s == 1) {
      if (str[i] == 'b') {
        ans = min(solve(i + 1, s), solve(i + 1, 2));
      } else {
        ans = min(solve(i + 1, s) + 1, solve(i + 1, 2));
      }
    } else if (s == 2) {
      if (str[i] == 'a') {
        ans = solve(i + 1, s);
      } else {
        ans = solve(i + 1, s) + 1;
      }
    }
    return dp[i][s] = ans;
  }
}
int main() {
  scanf(" %s", str);
  memset(dp, -1, sizeof dp);
  if (str[1] == 0) {
    printf("1\n");
  } else {
    printf("%d\n", strlen(str) - solve(0, 0));
  }
  return 0;
}
