#include <iostream>
#include <list>

using namespace std;

list<int> l;
int n;

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) l.push_back(i);

    int cur = 1;
    auto it = l.begin();
    while (l.size() > 1) {
        ++cur;
        ++it;

        // 每次在自增迭代器时判断一下是否到末尾
        if (it == l.end()) {
            it = l.begin();
        }

        if (cur % 3 == 0) {
            // printf("%d ", *it);
            it = l.erase(it);
            ++cur;
            if (it == l.end()) {
                it = l.begin();
            }
        }
    }

    printf("%d\n", l.front());

    return 0;
}

直接用STL的list模拟就好