function batchFund(uint16[] _day)
  payable
  external
  returns (bool) {
    require(_day.length <= 50);       
    require(msg.value >= _day.length);   
    uint256 amountPerDay = msg.value.div(_day.length);
    assert (amountPerDay.mul(_day.length) == msg.value);   
    for (uint8 i = 0; i < _day.length; i++){
      require(addContribution(msg.sender, amountPerDay, _day[i]));
    }
    return true;
  }