poj3006

普通的n^2的筛法居然比线性筛法快，不知道以后该用哪个了……

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 1000000

bool prime[maxn];

int main()
{
    //freopen("D:\\t.txt", "r", stdin);
    memset(prime, true, sizeof(prime));
    for (int i = 3; i <= 1000; i += 2)
        for (int j = 3; j <= maxn / i; j += 2)
            if (prime[i])
                prime[i * j] = false;
    for (int i = 4; i <= maxn; i += 2)
        prime[i] = false;
    prime[1] = prime[0] = false;

    int a, d, n;
    while (scanf("%d%d%d", &a, &d, &n) != EOF && !(a == 0 && d == 0 && n == 0))
    {
        int p;
        for (p = a; n > 0; p += d)
        {
            if (prime[p])
                n--;
        }
        printf("%d\n", p - d);
    }
    return 0;
}