线性筛

实现 
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#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e8 + 10;
bool isprime[MAXN];
int n, q, k;
vector<int> primes;
void init()
{
    memset(isprime, 1, sizeof(isprime));
    for (int i = 2; i <= n; i++)
    {
        if (isprime[i])
            primes.push_back(i);
        for (int p : primes)
        {
            if (p * i > n)
                break;
            isprime[p * i] = 0;
            if (i % p == 0)
                break;
        }
    }
}
int main()
{
    ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    cin >> n >> q;
    init();
    while(q--)
    {
        cin >> k;
        cout << primes[k - 1] << "\n";
    }
    return 0;
}