import java.util.Scanner;

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

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