import java.util.Scanner;
public class Main {
	int as,kl,o;
	String n,m;
	Scanner sc = new Scanner(System.in);
	public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	}
	public static void main(String[] args) {
		new Main().solve();
	
	}
} import java.util.Scanner; Scanner java.util public class Main {
	int as,kl,o;
	String n,m;
	Scanner sc = new Scanner(System.in);
	public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	}
	public static void main(String[] args) {
		new Main().solve();
	
	}
} Main int as as kl kl o; o String n n m; m Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	} solve {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	} n=sc.next() n sc.next() sc.next sc m=sc.next() m sc.next() sc.next sc String[]	date=n.split(""); date n.split("") n.split n "" String[]	dat=m.split(""); dat m.split("") m.split m "" for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	} o=0; o=0 o 0 o<n.length() o n.length() n.length n o++ o++ o {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	} {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	} if(date[o].equals(dat[o])) {
			as=as+1;
		} date[o].equals(dat[o]) date[o].equals date[o] date o dat[o] dat o {
			as=as+1;
		} as=as+1 as as+1 as 1 as=n.length()-as as n.length()-as n.length() n.length n as System.out.println(as) System.out.println System.out System System.out as public static void main(String[] args) {
		new Main().solve();
	
	} main {
		new Main().solve();
	
	} new Main().solve() new Main().solve new Main() String[] args args public class Main {
	int as,kl,o;
	String n,m;
	Scanner sc = new Scanner(System.in);
	public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	}
	public static void main(String[] args) {
		new Main().solve();
	
	}
} public class Main {
	int as,kl,o;
	String n,m;
	Scanner sc = new Scanner(System.in);
	public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	}
	public static void main(String[] args) {
		new Main().solve();
	
	}
} Main
import java.util.Scanner;
public class Main {
	int as,kl,o;
	String n,m;
	Scanner sc = new Scanner(System.in);
	public void solve() {	
	n=sc.next();
	m=sc.next();
	//String[] date=new String[n.length()];
	//String[] dat=new String[n.length()];
	//for(o=0;o<n.length();o++) {
	String[]	date=n.split("");
	String[]	dat=m.split("");
	//}
	for(o=0;o<n.length();o++) {
		//System.out.println(date[o]);
	//	System.out.println(dat[o]);
		if(date[o].equals(dat[o])) {
			as=as+1;
		}
	}
	as=n.length()-as;
	System.out.println(as);
	}
	public static void main(String[] args) {
		new Main().solve();
	
	}
}
