import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) char[] S = sc.next().toCharArray(); S sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc char[] T = sc.next().toCharArray(); T sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc int count = 0; count 0 for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		} 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]) {
				count++;
			}
		} {
			if (S[i] != T[i]) {
				count++;
			}
		} if (S[i] != T[i]) {
				count++;
			} S[i] != T[i] S[i] S i T[i] T i {
				count++;
			} count++ count System.out.println(count) System.out.println System.out System System.out count sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 入力値の取得
		char[] S = sc.next().toCharArray();
		char[] T = sc.next().toCharArray();
		
		int count = 0;
		
		// 結果の出力
		for (int i = 0; i < S.length; i++) {
			if (S[i] != T[i]) {
				count++;
			}
		}
		System.out.println(count);
		
		sc.close();
	}
}
