code:

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

int main() {
    long long n, ans = 0;
    
    cin >> n;
    
    for (int i = 1; i < n; i ++)
        for (int j = i + 1; j <= n; j ++)
            ans += __gcd(i, j);
    
    cout << ans;
    
    return 0;
}

最后6点TLE了，记录详情