import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    String S;
    String T;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    }
    
    //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    }
    
    //出力
    public void show(int answer) {
        System.out.println(answer);
    }

} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    String S;
    String T;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    }
    
    //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    }
    
    //出力
    public void show(int answer) {
        System.out.println(answer);
    }

} Main //フィールド
    Scanner sc; sc String S; S String T; T public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Main m = new Main(sc); m new Main(sc) m.show(m.solve()) m.show m m.solve() m.solve m sc.close() sc.close sc String[] args args //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    } Main {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    } this.sc = sc this.sc this this.sc sc this.S = sc.next() this.S this this.S sc.next() sc.next sc this.T = sc.next() this.T this this.T sc.next() sc.next sc Scanner sc sc //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    } solve {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    } int count = 0; count 0 if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        } !(S.equals(T)) (S.equals(T)) S.equals S T {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        } for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	} int i=0; int i=0; i 0 i<S.length() i S.length() S.length S i++ i++ i {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	} {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	} if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		} S.charAt(i) != T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T i {
        			count++;
        		} count++ count return count; count //出力
    public void show(int answer) {
        System.out.println(answer);
    } show {
        System.out.println(answer);
    } System.out.println(answer) System.out.println System.out System System.out answer int answer answer public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    String S;
    String T;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    }
    
    //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    }
    
    //出力
    public void show(int answer) {
        System.out.println(answer);
    }

} public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    String S;
    String T;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    }
    
    //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    }
    
    //出力
    public void show(int answer) {
        System.out.println(answer);
    }

} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    String S;
    String T;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.S = sc.next();
        this.T = sc.next();
    }
    
    //解答処理
    private int solve() {
        int count = 0;
        if (!(S.equals(T))) {
        	for (int i=0; i<S.length(); i++) {
        		if (S.charAt(i) != T.charAt(i)) {
        			count++;
        		}
        	}
        }
        
        return count;
    }
    
    //出力
    public void show(int answer) {
        System.out.println(answer);
    }

}
