print("Hello")
num1=int(input("Enter number (-1 to exit): "))
total=0
while num1!=-1:
    if num1<-1:
        print("You cannot input a negative number")
        num1=int(input("Enter number (-1 to exit): "))
    else:
        total=total+num1
        num1=int(input("Enter number (-1 to exit): "))
else:
    print (int(total))
    print ("Goodbye")