function mintToMax(address to) public onlyOwner returns (bool) {
        require(block.timestamp >= mintBegintime);
        require(mintMax > 0);

        uint256 value;
        if (mintPerday > 0) {
            uint256 currentMax = (block.timestamp - mintBegintime).mul(mintPerday) / (3600 * 24);
            value = currentMax.sub(mintTotal);
            uint256 leave = mintMax.sub(mintTotal);
            if (value > leave) {
                value = leave;
            }
        } else {
            value = mintMax.sub(mintTotal);
        }

        require(value > 0);
        mintTotal = mintTotal.add(value);
        _mint(to, value);
        emit Mint(to, value);
        return true;
    }