def add(a, b): return a + b

def subtract(a, b): return a - b

def multiply(a, b): return a * b

def divide(a, b): if b == 0: return "Cannot divide by zero" return a / b

while True: print("\nCalculator") print("1. Add") print("2. Subtract") print("3. Multiply") print("4. Divide") print("5. Exit")

choice = input("Enter choice (1-5): ")

if choice == "5":
    print("Goodbye!")
    break

num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))

if choice == "1":
    print("Result:", add(num1, num2))
elif choice == "2":
    print("Result:", subtract(num1, num2))
elif choice == "3":
    print("Result:", multiply(num1, num2))
elif choice == "4":
    print("Result:", divide(num1, num2))
else:
    print("Invalid choice!")