function refundContributors() public ended() onlyOwner() {
    bids[winner] = 0; 
    for (uint i = 0; i < accountsList.length;  i++) {
      if (bids[accountsList[i]] > 0) {
        uint refundValue = bids[accountsList[i]];
        bids[accountsList[i]] = 0;
        accountsList[i].transfer(refundValue); 
      }
    }
  }