import java.util.*;

public class Main {
    public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    }
} Main public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    } main {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    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 if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        } S.equals(T) S.equals S T {
            System.out.println(0);
        } System.out.println(0) System.out.println System.out System System.out 0 {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        } String[] sArray = new String[S.length()]; sArray new String[S.length()] S.length() S.length S String[] tArray = new String[T.length()]; tArray new String[T.length()] T.length() T.length T int count = 0; count 0 for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            } int i = 0; int i = 0; i 0 i < S.length() i S.length() S.length S i++ i++ i {
                sArray[i] = S.substring(i, i+1);
            } {
                sArray[i] = S.substring(i, i+1);
            } sArray[i] = S.substring(i, i+1) sArray[i] sArray i S.substring(i, i+1) S.substring S i i+1 i 1 for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            } int i = 0; int i = 0; i 0 i < T.length() i T.length() T.length T i++ i++ i {
                tArray[i] = T.substring(i, i+1);
            } {
                tArray[i] = T.substring(i, i+1);
            } tArray[i] = T.substring(i, i+1) tArray[i] tArray i T.substring(i, i+1) T.substring T i i+1 i 1 for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            } int i = 0; int i = 0; i 0 i < T.length() i T.length() T.length T i++ i++ i {
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            } {
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            } if(!sArray[i].equals(tArray[i])){
                    count++;
                } !sArray[i].equals(tArray[i]) sArray[i].equals(tArray[i]) sArray[i].equals sArray[i] sArray i tArray[i] tArray i {
                    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 ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    }
} public class Main {
    public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        String T = sc.next();
        if(S.equals(T)){
            System.out.println(0);
        } else {
            String[] sArray = new String[S.length()];
            String[] tArray = new String[T.length()];
            int count = 0;
            for(int i = 0;i < S.length();i++){
                sArray[i] = S.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                tArray[i] = T.substring(i, i+1);
            }
            for(int i = 0;i < T.length();i++){
                if(!sArray[i].equals(tArray[i])){
                    count++;
                }
            }
            System.out.println(count);
        }

    }
}
