

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	}

	public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	}
	
	
	
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {

	public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	}

	public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	}
	
	
	
} Main public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	} main {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String s=br.readLine().trim(); s br.readLine().trim() br.readLine().trim br.readLine() br.readLine br String t=br.readLine().trim(); t br.readLine().trim() br.readLine().trim br.readLine() br.readLine br algo(s,t) algo s t String[] args args public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	} algo {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	} int res=0; res 0 for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		} int i=0; int i=0; i 0 i<s.length() i s.length() s.length s i++ i++ i {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		} {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		} char c1=s.charAt(i); c1 s.charAt(i) s.charAt s i char c2=t.charAt(i); c2 t.charAt(i) t.charAt t i if(c1!=c2) {
				res++;
			} c1!=c2 c1 c2 {
				res++;
			} res++ res System.out.println(res) System.out.println System.out System System.out res String s s String t t public class Main {

	public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	}

	public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	}
	
	
	
} public class Main {

	public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	}

	public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	}
	
	
	
} Main


import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
	BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	String s=br.readLine().trim();
	String t=br.readLine().trim();
	algo(s,t);	
	
	}

	public static void algo(String s,String t) {
		int res=0;
		for(int i=0;i<s.length();i++) {
			char c1=s.charAt(i);
			char c2=t.charAt(i);
			if(c1!=c2) {
				res++;
			}
		}
		System.out.println(res);
		
		
	}
	
	
	
}
