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