#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
using i64 = long long;

constexpr int N = 51000000;
int f[N + 1], minp[N + 1], pos[N + 1];
vector<int> primes;

void chmax(auto &a, auto b) { a = max(a, b); }
int main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	
	int n;
	cin >> n;

	for (int i = 2; i <= n * (n - 1) / 2; i++) {
		if (!minp[i]) {
			primes.push_back(i);
			minp[i] = i;
		}
		for (int p : primes) {
			if (p > n * (n - 1) / 2 / i) {
				break;
			}
			minp[p * i] = p;
			if (i % p == 0) {
				break;
			}
		}
	}

	for (int i = 1; i <= n; i++) {
		f[i] = -i;
	}

	for (auto p : primes) {
		for (int i = 1; p * i <= n * (n - 1) / 2; i++) {
			f[p * i] += f[i];
		}
	}

	f[1] += n;

	for (int i = 2; i <= n * (n - 1) / 2; i++) {
		f[i] += f[i - 1];
		f[i] += n;
	}

	int ans = 0;

	ll m = n * (n-1) / 2;

	vector<int> vis_t(m+1, -1);

	ll ret = 0;
	//for (int i = 1;i <= m;++i) DE(i, f[i]);
	for (int i = 0;i <= m;++i) {
		if (vis_t[i] != -1) continue;
		ll ct = 0;
		for (int x = i;;x = f[x]) {
			//DE(x, vis_t[x], ct);
			if (vis_t[x] != -1) {
				if (vis_t[x] < ct) {
					chmax(ret, ct - vis_t[x]);
					break;
				}
			}
			vis_t[x] = ct++;
		}
	}
	cout << ret << '\n'; 
}