#include using namespace std; class Prime { private: vector div; public: Prime(long long n = 0) { for (long long i = 0; i <= n; ++i) div.emplace_back(i); for (long long i = 2; i <= n / i; ++i) if (div[i] == i) { for (long long j = i * i; j <= n; j += i) div[j] = i; } } bool isPrime(long long n) const { if (n <= 1) return false; if (n < (long long)div.size()) return div[n] == n; for (long long i = 2; i <= n / i; ++i) if (n % i == 0) return false; return true; } vector factor(long long n) const { vector res; for (long long i = 2; i <= n / i && n >= (long long)div.size(); ++i) { while (n % i == 0) { res.emplace_back(i); n /= i; } } if (n >= max((long long)div.size(), 2ll)) { res.emplace_back(n); } else { while (n > 1) { res.emplace_back(div[n]); n /= div[n]; } } sort(res.begin(), res.end()); return res; } vector primeFactor(long long n) const { vector res; for (long long i = 2; i <= n / i && n >= (long long)div.size(); ++i) { if (n % i) continue; res.emplace_back(i); while (n % i == 0) n /= i; } if (n >= max((long long)div.size(), 2ll)) { res.emplace_back(n); } else { while (n > 1) { long long d = div[n]; res.emplace_back(d); while (n % d == 0) n /= d; } } sort(res.begin(), res.end()); return res; } vector divisor(long long n) const { vector res; for (long long i = 1; i <= n / i; ++i) { if (n % i == 0) { res.emplace_back(i); if (i != n / i) res.emplace_back(n / i); } } sort(res.begin(), res.end()); return res; } }; int main() { long long n; cin >> n; long long x = n % 2 ? n : n / 2, res = 0; Prime prime; for (auto& i : prime.divisor(x)) res += i; cout << res << endl; }