java
import java.util.Scanner;
public class Main {
public static void turn(char[] a,int i) {
if(a[i] == '*') a[i] = 'o';
else a[i] = '*';
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
char[] a = sc.next().toCharArray();
char[] b = sc.next().toCharArray();
int c = a.length-1;
int sum = 0;
for(int i=0;i<c;i++) {
if(a[i]!=b[i]) {
sum++;
turn(a,i);
turn(a,i+1);
}
}
System.out.println(sum);
}
}