import java.util.*;
class Main{
    public static void main(String[]args){
        Scanner scanner = new Scanner(System.in);
        String[] S = scanner.nextLine().split("");
        String[] T = scanner.nextLine().split("");
        int cnt = 0;

        for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        }

        System.out.println(cnt);
        scanner.close();
    }
} import java.util.*; util.* java class Main{
    public static void main(String[]args){
        Scanner scanner = new Scanner(System.in);
        String[] S = scanner.nextLine().split("");
        String[] T = scanner.nextLine().split("");
        int cnt = 0;

        for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        }

        System.out.println(cnt);
        scanner.close();
    }
} Main public static void main(String[]args){
        Scanner scanner = new Scanner(System.in);
        String[] S = scanner.nextLine().split("");
        String[] T = scanner.nextLine().split("");
        int cnt = 0;

        for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        }

        System.out.println(cnt);
        scanner.close();
    } main {
        Scanner scanner = new Scanner(System.in);
        String[] S = scanner.nextLine().split("");
        String[] T = scanner.nextLine().split("");
        int cnt = 0;

        for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        }

        System.out.println(cnt);
        scanner.close();
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String[] S = scanner.nextLine().split(""); S scanner.nextLine().split("") scanner.nextLine().split scanner.nextLine() scanner.nextLine scanner "" String[] T = scanner.nextLine().split(""); T scanner.nextLine().split("") scanner.nextLine().split scanner.nextLine() scanner.nextLine scanner "" int cnt = 0; cnt 0 for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        } int i=0; int i=0; i 0 i<S.length i S.length S S.length i++ i++ i {
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        } {
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        } if(!(S[i].equals(T[i]))){
                cnt += 1;
            } !(S[i].equals(T[i])) (S[i].equals(T[i])) S[i].equals S[i] S i T[i] T i {
                cnt += 1;
            } cnt += 1 cnt 1 System.out.println(cnt) System.out.println System.out System System.out cnt scanner.close() scanner.close scanner String[]args args
import java.util.*;
class Main{
    public static void main(String[]args){
        Scanner scanner = new Scanner(System.in);
        String[] S = scanner.nextLine().split("");
        String[] T = scanner.nextLine().split("");
        int cnt = 0;

        for(int i=0;i<S.length;i++){
            if(!(S[i].equals(T[i]))){
                cnt += 1;
            }
        }

        System.out.println(cnt);
        scanner.close();
    }
}