Problem: Alice has a string s. She really likes the letter "a". She calls a string good if strictly more than half of the characters in that string are "a"s. For example "aaabb", "axaa" are good strings, and "baca", "awwwa", "" (empty string) are not.

Alice can erase some characters from her string s. She would like to know what is the longest string remaining after erasing some characters (possibly zero) to get a good string. It is guaranteed that the string has at least one "a" in it, so the answer always exists.

Input

The first line contains a string s (1 ≤ |s| ≤ 50) consisting of lowercase English letters. It is guaranteed that there is at least one "a" in s.

Output

Print a single integer, the length of the longest good string that Alice can get after erasing some characters from s.

Examples

Input


xaxxxxa


Output


3


Input


aaabaa


Output


6

Note

In the first example, it's enough to erase any four of the "x"s. The answer is 3 since that is the maximum number of characters that can remain.

In the second example, we don't need to erase any characters.

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;
public class Main{
    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while (!st.hasMoreTokens())
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }
        long[] nextArray(long n) {
            long[] a = new long[(int) n];
            for (int i = 0; i < n; i++) a[i] = nextLong();
            return a;
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
    static class FastWriter extends PrintWriter {
        FastWriter(){
            super(System.out);
        }
        void println(int[] array) {
            for(int i=0; i<array.length; i++) {
                print(array[i]+" ");
            }
            println();
        }
        void println(long [] array) {
            for(int i=0; i<array.length; i++) {
                print(array[i]+" ");
            }
            println();
        }
    }
    static int MOD=998244353;
    public static void main(String[] args){
        FastScanner in = new FastScanner();
        FastWriter out = new FastWriter();
        //int t=in.nextInt();
        int t=1;
        while (t-->0){
            String str=in.next();
            int acnt=0;
            for (int i = 0; i < str.length(); i++) {
                if(str.charAt(i)=='a'){
                    acnt++;
                }
            }
            if(2*acnt>str.length()){
                out.println(str.length());
            }else {
                out.println(2*acnt-1);
            }
        }
        out.close();
    }
    //Arrays.sort(a, (o1, o2) -> (o1[0] - o2[0]));
    static int diff(int num1,int num2) {
        String s1 = String.valueOf(num1);
        String s2 = String.valueOf(num2);
        if (s1.length() < s2.length()) {
            s1 = "0" + s1;
        }else if(s1.length()>s2.length()){
            s2="0"+s2;
        }
        int cnt=0;
        for (int i = 0; i < s1.length(); i++) {
            if(s1.charAt(i)!=s2.charAt(i)){
                cnt++;
            }
        }
        return cnt;
    }
    static int totalPrimeFactors(int n) {
        int cnt=0;
        while (n%2==0) {
            cnt++;
            n /= 2;
        }
        int num= (int) Math.sqrt(n);
        for (int i = 3; i <= num; i+= 2) {
            while (n%i == 0) {
                cnt++;
                n /= i;
                num=(int)Math.sqrt(n);
            }
        }
        if (n > 2){
            cnt++;
        }
        return cnt;
    }
    static char get(int i){
        return (char)(i+'a');
    }
    static boolean distinct(int num){
        HashSet<Integer> set=new HashSet<>();
        int len=String.valueOf(num).length();
        while (num!=0){
            set.add(num%10);
            num/=10;
        }
        return set.size()==len;
    }
    static int maxSubArraySum(int a[],int st,int en) {
        int max_s = Integer.MIN_VALUE, max_e = 0,ind=0,ind1=1;
        for (int i = st; i <= en; i++) {
            max_e+= a[i];
            if (max_s < max_e){
                max_s = max_e;
                ind=ind1;
            }
            if (max_e < 0){
                max_e = 0;
                ind1=i+1;
            }
        }
        if(st==0){
            return max_s;
        }
        if(ind==1){
            return a[0]+2*max_s;
        }else {
            return 2*max_s+maxSubArraySum(a,0,ind-1);
        }
        //return max_s;
    }
    static void segmentedSieve(ArrayList<Integer> res,int low, int high) {
        if(low < 2){
            low = 2;
        }
        ArrayList<Integer> prime = new ArrayList<>();
        simpleSieve(high, prime);
        boolean[] mark = new boolean[high - low + 1];
        for (int i = 0; i < mark.length; i++){
            mark[i] = true;
        }
        for (int i = 0; i < prime.size(); i++) {
            int loLim = (low / prime.get(i)) * prime.get(i);
            if (loLim < low){
                loLim += prime.get(i);
            }
            if (loLim == prime.get(i)){
                loLim += prime.get(i);
            }
            for (int j = loLim; j <= high; j += prime.get(i)) {
                mark[j - low] = false;
            }
        }
        for (int i = low; i <= high; i++) {
            if (mark[i - low]){
                res.add(i);
            }
        }
    }
    static void simpleSieve(int limit, ArrayList<Integer> prime) {
        int bound = (int)Math.sqrt(limit);
        boolean[] mark = new boolean[bound + 1];
        for (int i = 0; i <= bound; i++){
            mark[i] = true;
        }
        for (int i = 2; i * i <= bound; i++) {
            if (mark[i]) {
                for (int j = i * i; j <= bound; j += i){
                    mark[j] = false;
                }
            }
        }
        for (int i = 2; i <= bound; i++) {
            if (mark[i]){
                prime.add(i);
            }
        }
    }
    static int highestPowerOf2(int n) {
        if (n < 1){ return 0; }
        int res = 1;
        for (int i = 0; i < 8 * Integer.BYTES; i++) {
            int curr = 1 << i;
            if (curr > n){ break; }
            res = curr;
        }
        return res;
    }
    static int reduceFraction(int x, int y) {
        int d= gcd(x, y);
        return x/d+y/d;
    }
    static boolean subset(int[] ar,int n,int sum){
        if(sum==0){
            return true;
        }
        if(n<0||sum<0){
            return false;
        }
        return subset(ar,n-1,sum)||subset(ar,n-1,sum-ar[n]);
    }
    static boolean isPrime(int n){
        if(n<=1) return false;
        for(int i = 2;i<=Math.sqrt(n);i++){
            if (n % i == 0) return false;
        }
        return true;
    }
    static int gcd(int a, int b) {
        if (b == 0) return a;
        return gcd(b, a % b);
    }
    static long gcd(long a, long b) {
        if (b == 0) return a;
        return gcd(b, a % b);
    }
    static long lcm(long a, long b) {
        return (a * b) / gcd(a, b);
    }
    static int lcm(int a, int b) {
        return (a * b) / gcd(a, b);
    }
    static boolean isPowerOfTwo(int n) {
        if(n==0||n==1){return false;}
        double v = Math.log(n) / Math.log(2);
        return ((int)(Math.ceil(v)) == (int)(Math.floor(v)));
    }
    static boolean isPerfectSquare(int x){
        if (x >= 0) {
            int sr = (int)Math.sqrt(x);
            return ((sr * sr) == x);
        }
        return false;
    }
    static int lower_bound(int[] arr, int x) {
        int low_limit = 0, high_limit = arr.length, mid = -1;
        while (low_limit < high_limit) {
            mid = (low_limit + high_limit) / 2;
            if (arr[mid] >= x){
                high_limit = mid;
            }else{
                low_limit = mid + 1;
            }
        }
        return low_limit+1;
    }
    static int upper_bound(int[] arr, int x) {
        int low_limit = 0, high_limit = arr.length, mid = -1;
        while (low_limit < high_limit) {
            mid = (low_limit + high_limit) / 2;
            if (arr[mid] > x){
                high_limit = mid;
            }else{
                low_limit = mid + 1;
            }
        }
        return low_limit+1;
    }
    static int binarySearch(int[] ar,int n,int num){
        int low=0,high=n-1;
        while (low<=high){
            int mid=(low+high)/2;
            if(ar[mid]==num){
                return mid;
            }else if(ar[mid]>num){
                high=mid-1;
            }else {
                low=mid+1;
            }
        }
        return -1;
    }
}