import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	}
} import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	}
} Main public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	} main {
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	} Scanner s = new Scanner(System.in); s new Scanner(System.in) String ss = s.nextLine(); ss s.nextLine() s.nextLine s String st = s.nextLine(); st s.nextLine() s.nextLine s int count=0; count 0 char[] sstri= ss.toCharArray(); sstri ss.toCharArray() ss.toCharArray ss char[] tstri= st.toCharArray(); tstri st.toCharArray() st.toCharArray st for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		} int i=0; int i=0; i 0 i<sstri.length i sstri.length sstri sstri.length i++ i++ i {
			if(sstri[i] != tstri[i]){
				count++;
			}
		} {
			if(sstri[i] != tstri[i]){
				count++;
			}
		} if(sstri[i] != tstri[i]){
				count++;
			} sstri[i] != tstri[i] sstri[i] sstri i tstri[i] tstri i {
				count++;
			} count++ count System.out.print(count) System.out.print System.out System System.out count String[] args args public class Main{
	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	}
} public class Main{
	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	}
} Main
import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		
		String ss = s.nextLine();
		String st = s.nextLine();
		
		int count=0;
		
		char[] sstri= ss.toCharArray();
		char[] tstri= st.toCharArray();
		
		for(int i=0;i<sstri.length;i++){
			if(sstri[i] != tstri[i]){
				count++;
			}
		}
		System.out.print(count);
	}
}