num1 = float(input("Enter first number: ")) operator = input("Enter operator: ") num2 = float(input("Enter second number: "))
if operator == "+": print(num1 + num2) elif operator == "-": print(num1 - num2)
elif operator == "/": print(num1 / num2) elif operator == "*": print(num1 * num2) else: print("Error: Invalid operator."