import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	}

}

class MinorChange{
	char [] s;
	char [] t;
	private int count;
	
	MinorChange(String s,String t){
		this.s=s.toCharArray();
		this.t=t.toCharArray();
		
		count(this.s,this.t,s);
		
	}
	void count(char []s,char[]t,String str) {
		
		for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		}
		
	}
	public String toString() {
		return count+"";
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	}

} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	} main {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String s=scan.next(); s scan.next() scan.next scan String t=scan.next(); t scan.next() scan.next scan MinorChange a=new MinorChange(s,t); a new MinorChange(s,t) System.out.println(a.toString()) System.out.println System.out System System.out a.toString() a.toString a String[] args args class MinorChange{
	char [] s;
	char [] t;
	private int count;
	
	MinorChange(String s,String t){
		this.s=s.toCharArray();
		this.t=t.toCharArray();
		
		count(this.s,this.t,s);
		
	}
	void count(char []s,char[]t,String str) {
		
		for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		}
		
	}
	public String toString() {
		return count+"";
	}
} MinorChange char [] s; s char [] t; t private int count; count MinorChange(String s,String t){
		this.s=s.toCharArray();
		this.t=t.toCharArray();
		
		count(this.s,this.t,s);
		
	} MinorChange {
		this.s=s.toCharArray();
		this.t=t.toCharArray();
		
		count(this.s,this.t,s);
		
	} this.s=s.toCharArray() this.s this this.s s.toCharArray() s.toCharArray s this.t=t.toCharArray() this.t this this.t t.toCharArray() t.toCharArray t count(this.s,this.t,s) count this.s this this.s this.t this this.t s String s s String t t void count(char []s,char[]t,String str) {
		
		for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		}
		
	} count {
		
		for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		}
		
	} for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		} int i=0; int i=0; i 0 i<str.length() i str.length() str.length str i++ i++ i {
			if(s[i]!=t[i]) count++;
		} {
			if(s[i]!=t[i]) count++;
		} if(s[i]!=t[i]) count++; s[i]!=t[i] s[i] s i t[i] t i count++ count char []s s char[]t t String str str public String toString() {
		return count+"";
	} toString {
		return count+"";
	} return count+""; count+"" count "" public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	}

} public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();

        MinorChange a=new MinorChange(s,t);
        System.out.println(a.toString());
	}

}

class MinorChange{
	char [] s;
	char [] t;
	private int count;
	
	MinorChange(String s,String t){
		this.s=s.toCharArray();
		this.t=t.toCharArray();
		
		count(this.s,this.t,s);
		
	}
	void count(char []s,char[]t,String str) {
		
		for(int i=0;i<str.length();i++) {
			if(s[i]!=t[i]) count++;
		}
		
	}
	public String toString() {
		return count+"";
	}
}