class SimpleCalculator:
    def add(self, a, b):
        return a + b
 
    def subtract(self, a, b):
        return a - b
 
    def multiply(self, a, b):
        return a * b
 
    def divide(self, a, b):
        if b == 0:
            return "Error! Division by zero."
        return a / b
 
    def run(self):
        print("Simple Calculator")
        print("1. Add")
        print("2. Subtract")
        print("3. Multiply")
        print("4. Divide")
 
        while True:
            choice = input("Enter choice (1/2/3/4): ")
 
            if choice in ['1', '2', '3', '4']:
                try:
                    num1 = float(input("Enter first number: "))
                    num2 = float(input("Enter second number: "))
                except ValueError:
                    print("Invalid input! Please enter numeric values.")
                    continue
 
                if choice == '1':
                    print(f"Result: {self.add(num1, num2)}")
 
                elif choice == '2':
                    print(f"Result: {self.subtract(num1, num2)}")
 
                elif choice == '3':
                    print(f"Result: {self.multiply(num1, num2)}")
 
                elif choice == '4':
                    result = self.divide(num1, num2)
                    print(f"Result: {result}")
 
            else:
                print("Invalid choice! Please enter 1, 2, 3, or 4.")
 
            next_calculation = input("Do you want to perform another calculation? (yes/no): ")
            if next_calculation.lower() != 'yes':
                break
 
if __name__ == "__main__":
    calc = SimpleCalculator()
    calc.run()