import java.util.Scanner;

public class Main{
	static int res = 0;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	}
} import java.util.Scanner; Scanner java.util public class Main{
	static int res = 0;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	}
} Main static int res = 0; res 0 public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	} main {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int[] cnt = new int[2]; cnt new int[2] 2 String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
			cnt[s.charAt(i) - '0']++;
		} {
			cnt[s.charAt(i) - '0']++;
		} cnt[s.charAt(i) - '0']++ cnt[s.charAt(i) - '0'] cnt s.charAt(i) - '0' s.charAt(i) s.charAt s i '0' int ans = Math.min(cnt[0], cnt[1]) * 2; ans Math.min(cnt[0], cnt[1]) * 2 Math.min(cnt[0], cnt[1]) Math.min Math cnt[0] cnt 0 cnt[1] cnt 1 2 System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{
	static int res = 0;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	}
} public class Main{
	static int res = 0;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	}
} Main
import java.util.Scanner;

public class Main{
	static int res = 0;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int[] cnt = new int[2];
		String s = sc.nextLine();
		
		for(int i = 0; i < s.length(); i++) {
			cnt[s.charAt(i) - '0']++;
		}
		
		int ans = Math.min(cnt[0], cnt[1]) * 2;
		
		System.out.println(ans);	
	}
}