import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	}
} import java.util.*; util.* java public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	}
} Main public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	} main {
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) String s=sc.next(); s sc.next() sc.next sc String t=sc.next(); t sc.next() sc.next sc char[] s1=s.toCharArray(); s1 s.toCharArray() s.toCharArray s char[] t1=t.toCharArray(); t1 t.toCharArray() t.toCharArray t int cnt=0; cnt 0 for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		} int i=0; int i=0; i 0 i<s1.length i s1.length s1 s1.length i++ i++ i {
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		} {
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		} if(s1[i]!=t1[i])
			{
				cnt++;
			} s1[i]!=t1[i] s1[i] s1 i t1[i] t1 i {
				cnt++;
			} cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt sc.close() sc.close sc String[] args args public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	}
} public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	}
} Main
import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		String t=sc.next();
		char[] s1=s.toCharArray();
		char[] t1=t.toCharArray();
		int cnt=0;
		for(int i=0;i<s1.length;i++)
		{
			if(s1[i]!=t1[i])
			{
				cnt++;
			}
		}
		System.out.println(cnt);
		sc.close();
	}
}
