n calculate(i) {
                return function () {
                    screen.innerHTML = eval(screen.innerHTML);
                };
            }
        };
        </script>        
        <style>
            * {
                -webkit-touch-callout:none;
                -webkit-user-select:none;
                -moz-user-select:none;
                -ms-user-select:none;
                user-select:none;
            }
        
            html,body{
                width:100%;
    