contract Adoption {
  address[16] public adopters;
  uint[16] public prices;

  constructor() public {
    for (uint i=0;i<16;++i) {
      prices[i] = 0.001 ether;  
    }
  }

  // Adopting a pet
  function adopt(uint petId) public payable returns (uint) {
    require(petId >= 0 && petId <= 15);
    require(msg.value >= prices[petId]);

    prices[petId] *= 120;
    prices[petId] /= 100;

    adopters[petId] = msg.sender;
    return petId;
  }

  // Retrieving the adopters
  function getAdopters() public view returns (address[16] memory, uint[16] memory) {
    return (adopters,  prices);
  }
}
function getAdopters() public view returns (address[16] memory, uint[16] memory) {
  return (adopters,  prices);
}

// Retrieving the adopters