#include <iostream>
#include <vector>
int main()
{
    std::size_t N, P;
    std::cin >> N >> P;
    std::vector<bool> isprime(N + 1, true);
    std::size_t L = N - 1;
    for (std::size_t i = 2; i <= N; i++) {
        if (not isprime[i]) { continue; }
        if (2 * i > N) { L--; }
        for (std::size_t j = 2; i * j <= N; j++) { isprime[i * j] = false; }
    }
    std::cout << (P == 1 or (2 * P > N and isprime[P]) ? 1 : L) << std::endl;
    return 0;
}