import java.util.*;

public class Main {
	
//	public static String rev(int s) {
//		 String rev = new StringBuffer(s).reverse().toString();
//		 return rev;
//	}
	

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        }
         
        
        
        
	
} import java.util.*; util.* java public class Main {
	
//	public static String rev(int s) {
//		 String rev = new StringBuffer(s).reverse().toString();
//		 return rev;
//	}
	

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        }
         
        
        
        
	
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        } main {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String st1 = sc.next(); st1 sc.next() sc.next sc String st2 = sc.next(); st2 sc.next() sc.next sc int l1 = st1.length(); l1 st1.length() st1.length st1 char[] arr1 = st1.toCharArray(); arr1 st1.toCharArray() st1.toCharArray st1 char[] arr2 = st2.toCharArray(); arr2 st2.toCharArray() st2.toCharArray st2 int cnt = 0; cnt 0 for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		} int i = 0; int i = 0; i 0 i < l1 i l1 i++ i++ i {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		} {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		} if(arr1[i] != arr2[i]) {
				cnt++;
			} arr1[i] != arr2[i] arr1[i] arr1 i arr2[i] arr2 i {
				cnt++;
			} cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
	
//	public static String rev(int s) {
//		 String rev = new StringBuffer(s).reverse().toString();
//		 return rev;
//	}
	

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        }
         
        
        
        
	
} public class Main {
	
//	public static String rev(int s) {
//		 String rev = new StringBuffer(s).reverse().toString();
//		 return rev;
//	}
	

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        }
         
        
        
        
	
} Main
import java.util.*;

public class Main {
	
//	public static String rev(int s) {
//		 String rev = new StringBuffer(s).reverse().toString();
//		 return rev;
//	}
	

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String st1 = sc.next();
		String st2 = sc.next();
		int l1 = st1.length();
		char[] arr1 = st1.toCharArray();
		char[] arr2 = st2.toCharArray();
		int cnt = 0;
		for(int i = 0; i < l1; i++) {
			if(arr1[i] != arr2[i]) {
				cnt++;
			}
				
		}
       
        	
        	
        	System.out.println(cnt);
        }
         
        
        
        
	
}