function )
     * @param _ether_or_wei_value  input ethereum value (in wei or ether unit)
     * @return _num_of_tokens  number of tokens that can be bought with the input value
     * @return _exch_rate  current sale stage exchange rate (wei per now)
     * @return _current_sale_stage_index  current sale stage index
     */
    function simulate_token_sale(uint _ether_or_wei_value) public view 
	returns (uint256 _num_of_tokens, uint256 _exch_rate, uint256 _current_sale_stage_index) {
	if(sale_stage_index >=5 ) return (0,0,0);
	_exch_rate= sale_price_per_stage_wei_per_now[sale_stage_index];
        _current_sale_stage_index= sale_stage_index;
        
	if(_ether_or_wei_value>=1000000) 
	   _num_of_tokens= uint256( _ether_or_wei_value /  _exch_rate ); 
        else
	   _num_of_tokens= uint256( _ether_or_wei_value * WEI_PER_ETHER / _exch_rate ); 
    }