import java.util.*;
import java.util.function.*;
import java.math.*;
public class Main {
    public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	}
} import java.util.*; util.* java import java.util.function.*; function.* java.util import java.math.*; math.* java public class Main {
    public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	}
} Main public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	} main {
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	} Scanner s = new Scanner(System.in); s new Scanner(System.in) char[] S = s.next().toCharArray(); S s.next().toCharArray() s.next().toCharArray s.next() s.next s char[] T = s.next().toCharArray(); T s.next().toCharArray() s.next().toCharArray s.next() s.next s int ret = 0; ret 0 for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		} int i = 0; int i = 0; i 0 i < S.length i S.length S S.length i++ i++ i {
			if(S[i] != T[i]) {
				ret++;
			}
		} {
			if(S[i] != T[i]) {
				ret++;
			}
		} if(S[i] != T[i]) {
				ret++;
			} S[i] != T[i] S[i] S i T[i] T i {
				ret++;
			} ret++ ret System.out.println(ret) System.out.println System.out System System.out ret String[] args args public class Main {
    public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	}
} public class Main {
    public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	}
} Main
import java.util.*;
import java.util.function.*;
import java.math.*;
public class Main {
    public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		char[] S = s.next().toCharArray();
		char[] T = s.next().toCharArray();
		
		int ret = 0;
		for(int i = 0; i < S.length; i++) {
			if(S[i] != T[i]) {
				ret++;
			}
		}
		System.out.println(ret);
	}
}