求问

#include <iostream>
using namespace std;

const int N = 3e5 +5;
int n, cnt = 1, p[N] = {0, 2};

inline bool check(int num) {
	for (int i = 1; i <= cnt; i++) {
		if (p[i] * p[i] > num) return 1;
		if (! (num % p[i])) return 0;
	}
}
inline void search(int num) {
	if (cnt == n) {
        cout << p[n];
        exit(0);
    }
	if (check(num)) p[++cnt] = num;
	search(num + 1);
}

int main() {
	cin >> n;
	search(3);
}