# A simple calculator

def addition(x, y):
    return x + y

def subtraction(x, y):
    return x - y

def multiplication(x, y):
    return x * y

def division(x, y):
    return x / y


print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")

while True:
    # Take input from the user
    choice = input("Enter choice(1/2/3/4): ")

    # Check if choice is one of the four options
    if choice in ('1', '2', '3', '4'):
        num1 = float(input("Enter the first number: "))
        num2 = float(input("Enter the second number: "))

        if choice == '1':
            print(num1, "+", num2, "=", addition(num1, num2))

        elif choice == '2':
            print(num1, "-", num2, "=", subtraction(num1, num2))

        elif choice == '3':
            print(num1, "*", num2, "=", multiplication(num1, num2))

        elif choice == '4':
            print(num1, "/", num2, "=", division(num1, num2))
        break
    else:
        print("Invalid Input")
