1#include <iostream>2#include <cmath>3#include <vector>4#include <algorithm>5using namespace std;6 7long long solve1(int n) {8    vector<bool> p(n + 1, true);9    vector<long long> f(n + 1, 0), g(n + 1, 0);10    f[1] = 1;11    for (int i = 2; i * i <= n; i++) {12        if (p[i]) {13            vector<int> d;14            for (int k = i; k <= n; k *= i) d.push_back(k);15            reverse(d.begin(), d.end());16            for (int k : d) {17                for (int j = k; j <= n; j += k) {18                    if (p[j]) {19                        p[j] = false;20                        f[j] = i;21                        g[j] = k;22                    }23                }24            }25        }26    }27    for (int i = sqrt(n) + 1; i <= n; i++) {28        if (p[i]) {29            f[i] = i;30            g[i] = i;31        }32    }33    long long sum = 1;34    for (int i = 2; i <= n; i++) {35        f[i] = f[i / g[i]] * (g[i] * f[i] - 1) / (f[i] - 1);36        sum += f[i];37    }38    return sum;39}40 41long long solve2(int n) {42    long long sum = 0;43    for (int i = 1; i <= n; i++) {44        sum += i * (n / i);45    }46    return sum;47}48 49int main() {50    int n;51    cin >> n;52    cout << solve1(n) << endl;53    cout << solve2(n) << endl;54    return 0;55}

假设输入的 $n$ 是不超过 $1000000$ 的自然数，完成下面的判断题和单选题: