jj
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
int numOnes = 0;
int numZeros = 0;
for (int i = 0; i < input.length(); i++) {
if (input.charAt(i) == '1') {
numOnes++;
} else if (input.charAt(i) == '0') {
numZeros++;
} else {
throw new IllegalArgumentException("Input string should only contain 0s and 1s.");
}
}
int minSwaps = Math.min(numOnes, numZeros);
System.out.println(minSwaps);
}
}