TLE on Train Schedule

input/code.cpp:5:23: error: 'std::chrono' has not been declared
    5 | std::mt19937 rng(std::chrono::high_resolution_clock::now().time_since_epoch().count());
      |                       ^~~~~~

#include <iostream>
#include <random>
#include <cassert>

std::mt19937 rng(std::chrono::high_resolution_clock::now().time_since_epoch().count());

int random(int l, int r) {
  assert(l <= r);
  return std::uniform_int_distribution<int>(l, r)(rng);
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  int n = 100000;
  std::cout << n << '\n';
  int s = (int) sqrt(n);
  for (int i = 1; i <= n; i++) {
    std::cout << random(1, s) << ' ';
  }
  return 0;
}