import java.util.Scanner;
public class Main{

    public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    }
} import java.util.Scanner; Scanner java.util public class Main{

    public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    }
} Main public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    } main {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    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 c = S.length(); c S.length() S.length S int cnt=0; cnt 0 for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        } int i=0; int i=0; i 0 i<c i c i++ i++ i if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        } if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        } S.charAt(i)!=T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T i {
            cnt++;
        } cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt sc.close() sc.close sc final String args[] args public class Main{

    public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    }
} public class Main{

    public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    }
} Main
import java.util.Scanner;
public class Main{

    public static void main(final String args[]) {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        int c = S.length();
        int cnt=0;
    for(int i=0; i<c; i++)
        if(S.charAt(i)!=T.charAt(i)){
            cnt++;
        }
    System.out.println(cnt);
    sc.close();

    }
}