#include <bits/stdc++.h>

using namespace std;
const int N = 1000000;

int check[N];//元素值为0代表是素数
int prime[N];

int main() {
    int cnt = 0;
    for (int i = 2; i < N; i++) {
        //如果是素数
        if (!check[i]) prime[cnt++] = i;
        //筛出成倍的合数
        for (int j = 2 * i; j < N; j += i) check[j] = 1;
    }
    printf("%.2f", (double) clock() / CLOCKS_PER_SEC);
    return 0;
}