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.util.*;
import java.math.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

     //--------------->>>>IF YOU ARE HERE FOR QUICKSORT HACK THEN SORRY NO HACK FOR YOU<<<-------------------

public class a{ 
     static int[] count,count1,count2;
     static Node[] nodes;
     static long[] arr;
     static int[] dp,arrInt,darrInt;
     static char[] ch,ch1;
     static long[] darr,farr;
     static char[][] mat,mat1;
     static int[][] space;
     static boolean[][] vis;
     static long x,h;
     static long maxl;
     static double dec;
     static long mx = (long)1e10;
     static String s,s1,s2,s3,s4;
     static long minl;
     static int start_row;
     static int start_col;     
     static int end_row;     
     static int end_col;     
     static long mod = 998244353;
     // static int minl = -1;
     // static long n;
     static int n,n1,n2,q,r1,c1,r2,c2;
     static long a;
     static long b;
     static long c;
     static long d;
     static long y,z;
     static int m;
     static long k;
     static FastScanner sc;
     static String[] str,str1;
     static Set<Integer> set,set1,set2;
     static SortedSet<Long> ss;
     static List<Long> list,list1,list2,list3;
     static PriorityQueue<Integer> pq,pq1;
     static LinkedList<Node> ll;
     static Map<Integer,List<Integer>> map1;
     static Map<Long,Integer> map;
     static StringBuilder sb,sb1,sb2;
     static int index;
     static long[] sum;
     static int[] dx = {0,-1,0,1,-1,1,-1,1};
     static int[] dy = {-1,0,1,0,-1,-1,1,1};

     // public static void solve(){

     //    FastScanner sc = new FastScanner();
     //    // int t = sc.nextInt();
     //    int t = 1;
     //    for(int tt = 0 ; tt < t ; tt++){

     //        // s = sc.next();
     //        // s1 = sc.next();

     //        n = sc.nextInt();
     //        // m = sc.nextInt();
     //        // sb = new StringBuilder();
     //        // map = new HashMap<>();
     //        // q = sc.nextInt();
     //        k = sc.nextLong();
     //        // ch = sc.next().toCharArray();
     //        // boolean ans = false;
     //        // int charge = n;
     //        // int prev = 0;

     //        // count = new int[8];
           
     //        m = sc.nextInt();
     //        long ans = 0;
     //        long added = 0;
     //        for(int j = 0 ; j < m ; j++){

     //            int l = sc.nextInt();
     //            int r = sc.nextInt();
     //            long a = sc.nextLong();
     //            added += (r-l+1);
     //            ans += (r-l+1)*(a*a);

     //        }

     //        ans += (n-added)*(k*k);
     //        System.out.println(ans);
     //    }
        
     // }

     //--------------->>>>IF YOU ARE HERE FOR QUICKSORT HACK THEN SORRY NO HACK FOR YOU<<<-------------------
  
     public static void solve(){

        int n = ch.length;
        int count = 0;
        for(int i = 0 ; i  < n ; i++)
            if(ch[i] == 'a')
                count += 1;

        if(count > n/2){
            System.out.println(n);
            return;
        }
        System.out.println(2*count-1);    

     }
        
     public static void main(String[] args) {

            sc = new FastScanner();
            // Scanner sc = new Scanner(System.in);
            // int t = sc.nextInt();
            int t = 1;
            // int l = 1;
            while(t > 0){
                
                // n = sc.nextInt();
                // n = sc.nextLong();
                // k = sc.nextLong();
                // a = sc.nextLong();
                // b = sc.nextLong();
                // c = sc.nextLong();
                // d = sc.nextLong();

                // x = sc.nextLong();
                // y = sc.nextLong();
                // z = sc.nextLong();
                // d = sc.nextLong();
                
                // n = sc.nextLong();
                // n = sc.nextInt();
                // n = 3;
                // n1 = sc.nextInt();

                // m = sc.nextInt();
                // q = sc.nextInt();

                // k = sc.nextLong();
                // s = sc.next();

                ch = sc.next().toCharArray();
                // ch1 = sc.next().toCharArray();

                // arr = new long[n];
                // for(int i = 0 ; i < n ; i++){
                //     arr[i] = sc.nextLong();
                // }

                // arrInt = new int[n];
                // for(int i = 0 ; i < n ; i++){
                //     arrInt[i] = sc.nextInt();
                // }
                // x = sc.nextLong();
                // y = sc.nextLong();
                // ch = sc.next().toCharArray();
                // m = n;
                // darr = new long[m];
                // for(int i = 0 ; i < m ; i++){
                //     darr[i] = sc.nextLong();
                // }

                // m = n;
                // darrInt = new int[m];
                // for(int i = 0 ; i < m ; i++){
                //     darrInt[i] = sc.nextInt();
                // }

                // farr = new int[n];
                // for(int i = 0; i < n ; i++){
                //     farr[i] = sc.nextInt();
                // }

                // mat = new int[n][n];
                // for(int i = 0 ; i < n ; i++){
                //     for(int j = 0 ;  j < n ; j++){
                //         mat[i][j] = sc.nextInt();
                //     }
                // }

                // m = n;
                // mat = new char[n][m];
                // for(int i = 0 ; i < n ; i++){
                //     String s = sc.next();
                //     for(int j = 0 ; j < m ; j++){
                //         mat[i][j] = s.charAt(j);
                //     }
                // }

                // m = n;
                // mat1 = new char[n][m];
                // for(int i = 0 ; i < n ; i++){
                //     String s = sc.next();
                //     for(int j = 0 ; j < m ; j++){
                //         mat1[i][j] = s.charAt(j);
                //     }
                // }

                // str = new String[n];
                // for(int i = 0 ; i < n ; i++)
                //     str[i] = sc.next();

                // nodes = new Node[n];
                // for(int i = 0 ; i < n ;i++)
                //     nodes[i] = new Node(sc.nextInt(),(i));

                // System.out.println(solve()?"YES":"NO");
                 solve();       
                 // System.out.println(solve());
                 t -= 1;
            }

     }

     // public static dfs(int i){

     //    if(count[i] == 1)
     //        return;
     //    list = map.get(i);
     //    for(Integer j : list){
     //        if(j == i)
     //            continue;
     //        dfs(j);
     //    }
     // }

    public static int log(long n,long base){

         if(n == 0 || n == 1)
             return 0;

         if(n == base)
             return 1;

         double num = Math.log(n);
         double den = Math.log(base);

         if(den == 0)
             return 0;

         return (int)(num/den);
     }

    public static boolean isPrime(long n) { 
    // Corner cases 
        if (n <= 1)  
            return false; 

        if (n <= 3)  
            return true; 
      
        // This is checked so that we can skip  
        // middle five numbers in below loop 
        if (n%2 == 0 || n%3 == 0) 
            return false; 
      
        for (int i=5; i*i<=n; i=i+6) 
            if (n%i == 0 || n%(i+2) == 0) 
               return false; 
      
        return true; 
    } 

     public static long gcd(long a,long b){

        if(b%a == 0){
            return a;
        }
        return gcd(b%a,a);

     }

     public static void swap(int i,int j){
         long temp = arr[j];
         arr[j] = arr[i];
         arr[i] = temp;
     } 

    static final Random random=new Random();

    static void ruffleSortLong(long[] a) {
        int n=a.length;//shuffle, then sort 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            long temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }

    static void ruffleSortInt(int[] a) {
        int n=a.length;//shuffle, then sort 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            int temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }
    
    static void ruffleSortChar(char[] a) {
        int n=a.length;//shuffle, then sort 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            char temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }

    static class Node{
        Integer first;
        Integer second;
        Node(Integer f,Integer s){
            this.first = f;
            this.second = s;
        }
    }

     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[] readArray(int n) {
                        int[] a=new int[n];
                        for (int i=0; i<n; i++) a[i]=nextInt();
                        return a;
                }
                long nextLong() {
                        return Long.parseLong(next());
                }
        }

}