【小码匠自习室】ABC179-C：代码竟然没排倒数堪称一大奇迹

N

3

3

100

473

1000000

13969985

void coder_solution() {
    // 提升cin、cout效率
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n;
    cin >> n;
    long long ans = 0;
    for (int i = 1; i < n; ++i) {
        for(int j = 1; j * j <= i; ++j) {
            if (i % j == 0) {
                if (i / j == j) {
                    ans++;
                } else {
                    ans += 2;
                }
            }
        }
    }
    cout << ans;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    long long N;
    cin >> N;
    long long res = 0;
    for (long long a = 1; a < N; ++a) res += (N - 1)/ a;
    cout << res << endl;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
    long long N;
    cin >> N;
    long long res = 0;
    for (long long A = 1; A * A < N; ++A) ++res;
    for (long long A = 1; A * A < N; ++A) {
        long long num = max((N - 1) / A - A, 0LL);
        res += num * 2;
    }
    cout << res << endl;
}