0pts，求调，玄关

#include <bits/stdc++.h>
using namespace std;
bool st[10000];
long long l, r, ans = 0;

void WePHe() {
	for (long long i = l; i <= r; i++) {
		if (st[i]) {
			continue;
		}
		ans++;
		for (long long j = i + i; j <= r; j += i) {
			st[j] = true;
		}
	}
}

/*方块树下方块果，方块树下你和我*/
int main() {
	cin >> l >> r;
	WePHe();
	cout << ans << endl;

	return 0;
}