代码

#include <bits/stdc++.h>
using namespace std;
int l, r, cnt;
bool vis[10000010];

int main() {
	cin >> l >> r;
	vis[1] = 1;
	for (int i = 2; i * i <= r; i++) {
		if (!vis[i]) {
			for (int j = 2; i * j <= r; j++) {
				vis[i * j] = 1;
			}
		}
	}
	for (int i = l; i <= r; i++) {
		if (!vis[i])
			cnt++;
	}
	cout << cnt;
	return 0;
}

测点