  function burnTokens (uint256 _value) public returns (bool success) {
    if (_value > accounts [msg.sender]) return false;
    else if (_value > 0) {
      accounts [msg.sender] = safeSub (accounts [msg.sender], _value);
      tokensCount = safeSub (tokensCount, _value);
      return true;
    } else return true;
  }