Croseta

/* [A][M][C][B][N] / [K][R][I][P][6][8] */
#include <bits/stdc++.h>
#pragma warning(disable : 4996 4267 4068)
using namespace std;
template<typename type>
using matrix = vector<vector<type>>;
typedef long long ll;
const char sp = ' ', nl = '\n';
const int MOD = 1000000007;

ll compute(ll n) {
    ll cnt(0);
    while (n) {
        cnt += n;
        if (n == 1) break;
        n = max(n / 3 - 1, 0ll) + 1;
    }
    return cnt;
}

ll find(ll n) {
    int st = 1, dr = 1.5e9, m;
    while (st <= dr) {
        m = (st + dr) / 2;
        if (compute(m) == n)
            return m;
        else {
            if (compute(m) < n)
                st = m + 1;
            else
                dr = m - 1;
        }
    }
}

int main() {
    ios::sync_with_stdio(NULL);
    cin.tie(nullptr), cout.tie(nullptr);
    (void)!freopen("croseta.in", "r", stdin);
    (void)!freopen("croseta.out", "w", stdout);
    ll n;
    cin >> n;
    cout << find(n / 2);
}