import java.util.Scanner;

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

public class Main {
	public static void main(String args[]) {
		Scanner stdIn = new Scanner(System.in);
		char[] S = stdIn.next().toCharArray();
		char[] T = stdIn.next().toCharArray();
		
		int cnt = 0;
		
		for(int i = 0; i < S.length; i ++) {
			if(S[i] != T[i]) {
				cnt ++;
			}
		}
		
		System.out.println(cnt);
	}
}