09. Multiply by 2

function multiplay(input){

    let command = Number(input.shift());
    let sum = 0;

    while(true){
        if(command < 0){
            console.log("Negative number!");
            break;
        }

        sum = command * 2;
        console.log(sum.toFixed(2));
        command = input.shift();
    }
}