How to speed-up loading of 15M integers from file stream?

I have an array of precomputed integers, it's fixed size of 15M values. I need to load these values at the program start. Currently it takes up to 2 mins to load, file size is ~130MB. Is it any way to speed-up loading. I'm free to change save process as well.

std::array<int, 15000000> keys;

std::string config = "config.dat";

// how array is saved
std::ofstream out(config.c_str());
std::copy(keys.cbegin(), keys.cend(),
  std::ostream_iterator<int>(out, "\n"));

// load of array
std::ifstream in(config.c_str());
std::copy(std::istream_iterator<int>(in),
  std::istream_iterator<int>(), keys.begin());
in_ranks.close();

Thanks in advance.

SOLVED. Used the approach proposed in accepted answer. Now it takes just a blink.

Thanks all for your insights.