import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String t = sc.next();

        char[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    }
} import java.util.Scanner; Scanner 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[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String t = sc.next();

        char[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    } main {
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String t = sc.next();

        char[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    } 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[] sChar = new char[s.length()]; sChar new char[s.length()] s.length() s.length s char[] tChar = new char[t.length()]; tChar new char[t.length()] t.length() t.length t for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        } int i = 0; int i = 0; i 0 i<s.length() i s.length() s.length s i++ i++ i {
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        } {
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        } sChar[i] = s.charAt(i) sChar[i] sChar i s.charAt(i) s.charAt s i tChar[i] = t.charAt(i) tChar[i] tChar i t.charAt(i) t.charAt t i int count = 0; count 0 for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        } int j = 0; int j = 0; j 0 j<s.length() j s.length() s.length s j++ j++ j {
            if(sChar[j] != tChar[j]){
                count++;
            }
        } {
            if(sChar[j] != tChar[j]){
                count++;
            }
        } if(sChar[j] != tChar[j]){
                count++;
            } sChar[j] != tChar[j] sChar[j] sChar j tChar[j] tChar j {
                count++;
            } count++ count System.out.println(count) System.out.println System.out System System.out count 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[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    }
} public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String t = sc.next();

        char[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    }
} Main
import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String t = sc.next();

        char[] sChar = new char[s.length()];
        char[] tChar = new char[t.length()];

        for(int i = 0; i<s.length(); i++){
            sChar[i] = s.charAt(i);
            tChar[i] = t.charAt(i);
        }

        int count = 0;
        for(int j = 0; j<s.length(); j++){
            if(sChar[j] != tChar[j]){
                count++;
            }
        }
        System.out.println(count);

    }
}