KStatWithStandardPartition

#include <algorithm>
#include <iostream>
#include <vector>

int KStat(std::vector<int>& v, int k) {
  int l = 0, r = v.size();
  while (true) {
    std::swap(v[(l + r) / 2], v[r - 1]);
    const int& x = v[r - 1];
    const auto i = std::partition(v.begin() + l, v.begin() + r - 1, [&x](const int& e) -> bool {
      return e < x;
    });
    std::swap(*i, v[r - 1]);
    const int p = i - v.begin();
    if (p == k) return v[k];
    if (p > k) {
      r = p;
    } else {
      l = p + 1;
    }
  }
}

int main() {
  int n = 0, k = 0;
  std::cin >> n >> k;
  std::vector<int> v(n, 0);
  for (int i = 0; i < n; ++i) {
    std::cin >> v[i];
  }
  std::cout << KStat(v, k);
  return 0;
}