import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class VirusReplication {

	/**
	 * @param args
	 * @throws IOException
	 */
	public static void main(String[] args) throws IOException {
		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
		char[] s1 = bf.readLine().toCharArray();
		char[] s2 = bf.readLine().toCharArray();



		int startidx = -1;
		int endidx = -1;

		for (int i = 0; i < s2.length && i < s1.length; i++) {
			if (s1[i] != s2[i]) {
				startidx = i;
				break;
			}
		}

		if (startidx == -1 && s1.length != s2.length) {
			if (s1.length < s2.length)
				System.out.println(Math.max(s1.length, s2.length) - Math.min(s1.length, s2.length));
			else
				System.out.println(0);
			return;
		}


		for (int i = s1.length - 1, j = s2.length - 1; i >= 0 && j >= 0; i--, j--) {
			if (s1[i] != s2[j]) {
				endidx = j;
				break;
			}
		}

		if (endidx == -1 && s1.length != s2.length) {
			if (s1.length < s2.length)
				System.out.println(Math.max(s1.length, s2.length) - Math.min(s1.length, s2.length));
			else
				System.out.println(0);
			return;
		}

		if (endidx == -1 && startidx == -1) {
			System.out.println(0);
			return;
		}




		System.out.println(endidx - startidx + 1);

	}

}