import java.util.*;

public class Main {
    public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    }
} 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 t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    }
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    } main {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String t = sc.next(); t sc.next() sc.next sc char[] m1 = new char[s.length()]; m1 new char[s.length()] s.length() s.length s char[] m2 = new char[s.length()]; m2 new char[s.length()] s.length() s.length s int count = 0; count 0 for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        } {
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        } m1[i] = s.charAt(i) m1[i] m1 i s.charAt(i) s.charAt s i m2[i] = t.charAt(i) m2[i] m2 i t.charAt(i) t.charAt t i if(!(m1[i] == m2[i]))
            count++; !(m1[i] == m2[i]) (m1[i] == m2[i]) m1[i] m1 i m2[i] m2 i count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
        String t = sc.next();
        char[] m1 = new char[s.length()];
        char[] m2 = new char[s.length()];
        int count = 0;
        for(int i = 0; i < s.length(); i++){
            m1[i] = s.charAt(i);
            m2[i] = t.charAt(i);
            if(!(m1[i] == m2[i]))
            count++;
        }
        System.out.println(count);
    }
}