注意会爆int。

/*
 project euler problem 10: 求小于 2000000 的所有质数之和
 answer: 
*/

#include<bits/stdc++.h>

using namespace std;

const int N = 2000000 + 1;
int st[N];

int main(void)
{
    vector<int> primes;

    for (int i = 2; i < N; ++i)
    {
        if (st[i]) continue;

        primes.push_back(i);

        for (int j = 2; j * i < N; ++ j) st[j * i] = 1;
    }

    long long ans = 0;
    for (auto x: primes) ans += (long long) x;

    cout << ans << endl;

    return 0;
}