#include <algorithm>
#include <iostream>
#include <vector>
#include <set>
#include <map>

using namespace std;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n, m;
	cin >> n >> m;
	vector<long long>v(15485864);
	for (int i = 0; i <= 15485863; ++i) {
		v[i] = i;
	}
	for (int i = 0; i <= 15485863; ++i) {
		if (v[i] != 0) {
			for (int j = 2 * i; j <= 15485863; j += i)
				v[j] = 0;
		}
	}

	long long res = 0; int ptr = 0;
	for (int i = 2; ptr < m; ++ptr) {
		if (v[i] == 0) {
            continue;
		}

			if (ptr >= n)
				res += 1;
	}
	cout << res;
}