import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    } main {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.next(); S sc.next() sc.next sc String[] s = S.split(""); s S.split("") S.split S "" int count0 = 0; count0 0 int count1 = 0; count1 0 for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        } int i=0; int i=0; i 0 i<s.length i s.length s s.length i++ i++ i {
            if(s[i].equals("0")) count0++;
            else count1++;
        } {
            if(s[i].equals("0")) count0++;
            else count1++;
        } if(s[i].equals("0")) count0++;
            else count1++; s[i].equals("0") s[i].equals s[i] s i "0" count0++ count0 count1++ count1 if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2); count0 >= count1 count0 count1 System.out.println(count1*2) System.out.println System.out System System.out count1*2 count1 2 System.out.println(count0*2) System.out.println System.out System System.out count0*2 count0 2 String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    }
} Main
import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String[] s = S.split("");
        int count0 = 0;
        int count1 = 0;
        for(int i=0; i<s.length; i++) {
            if(s[i].equals("0")) count0++;
            else count1++;
        }
        if(count0 >= count1) System.out.println(count1*2);
        else System.out.println(count0*2);
    }
}
