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