<div class="custom-form">
                    <h2 class="custom-form-heading">Enter Details <a class="form-popup-close back-btn">Close</a></h2>

                    <div class="custom-form-group">
                        <input class="amountBuy" placeholder="enter amount to buy in wei" />
                    </div>
                    <div class="custom-form-group">
                        <button class="form-group-btn">Buy</button>
                    </div>
                    <div class="result"></div>
                </div>
            </div>
        </div>

// addUsers(msg.sender);

    if (users.length>0){
            uint count=0;
        for (uint a=0;a<users.length;a++)
        {
        if (users[a]==msg.sender){
        count=count+1;
        }
        }
        if (count==0){
            users.push(msg.sender);
        }

    }
    else{
        users.push(msg.sender);
    }


}