function getBalance(address _address) view public returns (uint256) {
        uint256 minutesCount = now.sub(joined[_address]).div(1 minutes);
        
        
        
        
        
        uint256 userROIMultiplier = 2**(minutesCount / 60);
        
        uint256 percent;
        uint256 balance;
        
        for(uint i=1; i<userROIMultiplier; i=i*2){
            
            
            
            
            
            percent = investments[_address].mul(step).div(1000) * i;
            balance += percent.mul(60).div(1440);
            
        }
        
        
        percent = investments[_address].mul(step).div(1000) * userROIMultiplier;
        balance += percent.mul(minutesCount % 60).div(1440);

        return balance;
    }