import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    }

    public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    }

    public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    } main {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc String t = sc.nextLine(); t sc.nextLine() sc.nextLine sc System.out.println(calc(s, t)) System.out.println System.out System System.out calc(s, t) calc s t String[] args args public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    } calc {
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    } int answer = 0; answer 0 for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        } {
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        } if(s.charAt(i) != t.charAt(i)){
                answer++;
            } s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {
                answer++;
            } answer++ answer return answer; answer String s s String t t public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    }

    public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    }

    public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        String t = sc.nextLine();
        System.out.println(calc(s, t));
    }

    public static int calc(String s, String t){
        int answer = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                answer++;
            }
        }
        return answer;
    }
}
