#include <bits/stdc++.h>
using namespace std;
long long int MOD = 1e9 + 7;
long long int INF = 1e18;
long long int sub(long long int a, long long int b, long long int p = MOD) {
  return ((a % p) - (b % p) + p) % p;
}
long long int mult(long long int a, long long int b, long long int p = MOD) {
  return ((a % p) * (b % p)) % p;
}
long long int add(long long int a, long long int b, long long int p = MOD) {
  return (a % p + b % p) % p;
}
long long int fpow(long long int n, long long int k, long long int p = MOD) {
  long long int r = 1;
  while (k > 0) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
    k = k >> 1;
  }
  return r;
}
long long int inv(long long int a, long long int p = MOD) {
  return fpow(a, p - 2, p);
}
long long int power(long long int a, long long int b) {
  long long int ans = 1;
  long long int i;
  for (i = 1; i < b + 1; i++) {
    ans *= a;
  }
  return ans;
}
long long int fdiv(long long int a, long long int b, long long int p = MOD) {
  long long int yinv = inv(b);
  long long int ans = (a * yinv) % p;
  return ans;
}
unsigned long long int I1018 = 1000000000000000000;
const unsigned long long int I10e5 = 100000;
const long long int I10e6 = 1e6;
template <typename T>
istream &operator>>(istream &in, vector<T> &a) {
  for (auto &item : a) {
    in >> item;
  }
  return in;
}
template <typename T, typename U>
ostream &operator<<(ostream &out, pair<T, U> &a) {
  cout << a.first << " " << a.second;
  return out;
}
template <typename T, typename U>
istream &operator>>(istream &out, pair<T, U> &a) {
  cin >> a.first >> a.second;
  return out;
}
template <typename T, typename U>
ostream &operator<<(ostream &out, map<T, U> &a) {
  for (auto &item : a) {
    out << item << endl;
  }
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, vector<T> &a) {
  for (auto &item : a) {
    out << item << " ";
  }
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, vector<vector<T>> &a) {
  for (auto &item : a) {
    out << item << "\n";
  }
  return out;
}
std::vector<bool> is_prime;
std::vector<long long int> primes;
void sieve(long long int n) {
  is_prime.resize(n + 2, true);
  primes.clear();
  long long int p;
  for (p = 2; p * p <= n; p++) {
    if (is_prime[p]) {
      long long int i;
      for (i = p * p; i <= n; i += p) {
        is_prime[i] = false;
      }
    }
  }
  is_prime[0] = is_prime[1] = false;
  long long int i;
  for (i = 2; i <= n; i++) {
    if (is_prime[i]) {
      primes.emplace_back(i);
    }
  }
}
map<long long int, long long int> prime_factors(long long int n) {
  map<long long int, long long int> s;
  long long int i;
  long long int tc = 0;
  while (n % 2 == 0) {
    tc++;
    n /= 2;
  }
  if (tc > 0) {
    s[2] = tc;
  }
  for (i = 3; i <= sqrt(n); i += 2) {
    tc = 0;
    while (n % i == 0) {
      tc++;
      n /= i;
    }
    if (tc > 0) {
      s[i] = tc;
    }
  }
  if (n > 2) {
    s[n] += 1;
  }
  return s;
}
std::vector<long long int> fact_vec;
void fact_fun(long long int n) {
  fact_vec.resize(n + 10);
  long long int i;
  fact_vec[0] = 1;
  for (i = 1; i <= n + 2; i++) {
    fact_vec[i] = (fact_vec[i - 1] * i) % MOD;
  }
}
long long int npr(long long int n, long long int r) {
  long long int ans = fact_vec[n];
  ans /= fact_vec[n - r];
  return ans;
}
long long int ncr(long long int n, long long int r) {
  long long int ans = fact_vec[n];
  ans = fdiv(ans, fact_vec[n - r]);
  ans = fdiv(ans, fact_vec[r]);
  return ans;
}
long long int nc2(long long int n) { return (n * (n - 1)) / 2; }
set<long long int> s;
int main() {
  long long int i, j;
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long int n, k;
  cin >> n >> k;
  for (i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      s.insert(i);
      s.insert(n / i);
    }
  }
  if (k > s.size()) {
    cout << -1 << endl;
  } else {
    j = 1;
    for (auto p : s) {
      if (j == k) {
        cout << p << endl;
        return 0;
      }
      j++;
    }
  }
}

### Prompt

Your challenge is to write a CPP solution to the following problem:

You are given two integers n and k. Find k-th smallest divisor of n, or report that it doesn't exist.

Divisor of n is any such natural number, that n can be divided by it without remainder.

Input

The first line contains two integers n and k (1 ≤ n ≤ 1015, 1 ≤ k ≤ 109).

Output

If n has less than k divisors, output -1.

Otherwise, output the k-th smallest divisor of n.

Examples

Input

4 2


Output

2


Input

5 3


Output

-1


Input

12 5


Output

6

Note

In the first example, number 4 has three divisors: 1, 2 and 4. The second one is 2.

In the second example, number 5 has only two divisors: 1 and 5. The third divisor doesn't exist, so the answer is -1.

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
long long int MOD = 1e9 + 7;
long long int INF = 1e18;
long long int sub(long long int a, long long int b, long long int p = MOD) {
  return ((a % p) - (b % p) + p) % p;
}
long long int mult(long long int a, long long int b, long long int p = MOD) {
  return ((a % p) * (b % p)) % p;
}
long long int add(long long int a, long long int b, long long int p = MOD) {
  return (a % p + b % p) % p;
}
long long int fpow(long long int n, long long int k, long long int p = MOD) {
  long long int r = 1;
  while (k > 0) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
    k = k >> 1;
  }
  return r;
}
long long int inv(long long int a, long long int p = MOD) {
  return fpow(a, p - 2, p);
}
long long int power(long long int a, long long int b) {
  long long int ans = 1;
  long long int i;
  for (i = 1; i < b + 1; i++) {
    ans *= a;
  }
  return ans;
}
long long int fdiv(long long int a, long long int b, long long int p = MOD) {
  long long int yinv = inv(b);
  long long int ans = (a * yinv) % p;
  return ans;
}
unsigned long long int I1018 = 1000000000000000000;
const unsigned long long int I10e5 = 100000;
const long long int I10e6 = 1e6;
template <typename T>
istream &operator>>(istream &in, vector<T> &a) {
  for (auto &item : a) {
    in >> item;
  }
  return in;
}
template <typename T, typename U>
ostream &operator<<(ostream &out, pair<T, U> &a) {
  cout << a.first << " " << a.second;
  return out;
}
template <typename T, typename U>
istream &operator>>(istream &out, pair<T, U> &a) {
  cin >> a.first >> a.second;
  return out;
}
template <typename T, typename U>
ostream &operator<<(ostream &out, map<T, U> &a) {
  for (auto &item : a) {
    out << item << endl;
  }
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, vector<T> &a) {
  for (auto &item : a) {
    out << item << " ";
  }
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, vector<vector<T>> &a) {
  for (auto &item : a) {
    out << item << "\n";
  }
  return out;
}
std::vector<bool> is_prime;
std::vector<long long int> primes;
void sieve(long long int n) {
  is_prime.resize(n + 2, true);
  primes.clear();
  long long int p;
  for (p = 2; p * p <= n; p++) {
    if (is_prime[p]) {
      long long int i;
      for (i = p * p; i <= n; i += p) {
        is_prime[i] = false;
      }
    }
  }
  is_prime[0] = is_prime[1] = false;
  long long int i;
  for (i = 2; i <= n; i++) {
    if (is_prime[i]) {
      primes.emplace_back(i);
    }
  }
}
map<long long int, long long int> prime_factors(long long int n) {
  map<long long int, long long int> s;
  long long int i;
  long long int tc = 0;
  while (n % 2 == 0) {
    tc++;
    n /= 2;
  }
  if (tc > 0) {
    s[2] = tc;
  }
  for (i = 3; i <= sqrt(n); i += 2) {
    tc = 0;
    while (n % i == 0) {
      tc++;
      n /= i;
    }
    if (tc > 0) {
      s[i] = tc;
    }
  }
  if (n > 2) {
    s[n] += 1;
  }
  return s;
}
std::vector<long long int> fact_vec;
void fact_fun(long long int n) {
  fact_vec.resize(n + 10);
  long long int i;
  fact_vec[0] = 1;
  for (i = 1; i <= n + 2; i++) {
    fact_vec[i] = (fact_vec[i - 1] * i) % MOD;
  }
}
long long int npr(long long int n, long long int r) {
  long long int ans = fact_vec[n];
  ans /= fact_vec[n - r];
  return ans;
}
long long int ncr(long long int n, long long int r) {
  long long int ans = fact_vec[n];
  ans = fdiv(ans, fact_vec[n - r]);
  ans = fdiv(ans, fact_vec[r]);
  return ans;
}
long long int nc2(long long int n) { return (n * (n - 1)) / 2; }
set<long long int> s;
int main() {
  long long int i, j;
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long int n, k;
  cin >> n >> k;
  for (i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      s.insert(i);
      s.insert(n / i);
    }
  }
  if (k > s.size()) {
    cout << -1 << endl;
  } else {
    j = 1;
    for (auto p : s) {
      if (j == k) {
        cout << p << endl;
        return 0;
      }
      j++;
    }
  }
}

```