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

class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] str = br.readLine().split(" ");
		br.close();
		int num = Integer.parseInt(str[0]) - 1;
		int len = Integer.parseInt(str[1]);

		long count = 0;

		if (num * 2 <= len) {
			count += len - num * 2 + 1;
		}
		int i,j;
		for (i = 3; num * i <= len; i += 2) {
			boolean flag = true;
			for (j = 3; j * j <= i; j += 2) {
				if (i % j == 0) {
					flag = false;
					break;
				}
			}
			if (flag) {
				count += len - num * i + 1;
			}
		}
		System.out.println(count);
	}
}