#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100000 + 10;
int n;
int m;
char s[MAXN];
int x[MAXN], y[MAXN];
int main() {
  while (~scanf("%s", s)) {
    int len = strlen(s);
    int max1 = 0, max2 = 0, max3 = 0, max4 = 0, max5 = 0;
    for (int i = 0; i < len; i++) {
      if (s[i] == 'a')
        max1++;
      else if (s[i] == 'b')
        x[i] = max1;
    }
    for (int i = len - 1; i >= 0; i--) {
      if (s[i] == 'a')
        max2++;
      else
        y[i] = max2;
    }
    int maxn = 0;
    for (int i = 0; i < len; i++) {
      if (s[i] == 'b') {
        int ans = x[i];
        for (int j = i; j < len; j++) {
          if (s[j] == 'b') {
            ans++;
            maxn = max(maxn, ans + y[j]);
          }
        }
      }
    }
    printf("%d\n", max(maxn, max1));
  }
}
