// Arup Guha
// 10/26/2013
// Solution to 2013 NCPC Problem E: Virus Replication

import java.util.*;

public class virus {

	public static void main(String[] args) {

		Scanner stdin = new Scanner(System.in);
		String s1 = stdin.next();
		String s2 = stdin.next();

		// Greedy match from both sides.
		int i = 0, j = 0;
		while (i < s1.length() && i < s2.length() && s1.charAt(i) == s2.charAt(i)) i++;
		while (j < s1.length() && j < s2.length() && s1.charAt(s1.length()-1-j) == s2.charAt(s2.length()-1-j)) j++;
		j = s2.length() - j;

		// Initial answer is what's left.
		int ans = Math.max(j-i, 0);

		// But, check with lengths of both strings!
		System.out.println(Math.max(ans, s2.length()-s1.length()));
	}
}