PAIRLCM TS10 PTNK 2020-2021

#define task "PAIRLCM"

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

using ll = long long;
using ld = long double;

constexpr int N = 1e5 + 5;
int n;

void Read()
{
    cin >> n;
}

bool IsOdd(int v)
{
    return v & 1;
}

ll lcm(int x, int y)
{
    return 1ll * x * y / __gcd(x, y);
}

void Solve()
{
    if (IsOdd(n))
        cout << 1ll * (n / 2) * (n / 2 + 1);
    else
    {
        ll v = n / 2;
        if (n / 2 > 1)
            v = max(v, lcm(n / 2 - 1, n / 2 + 1));
        if (n / 2 > 2)
            v = max(v, lcm(n / 2 - 2, n / 2 + 2));

        cout << v;
    }
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen(task ".INP", "r"))
    {
        freopen(task ".INP", "r", stdin);
        freopen(task ".OUT", "w", stdout);
    }

    Read();
    Solve();
}