class pckg:
    def __init__(self):
        print("Hello Welsomce to ustav Library.")
        
    def sum(num1,num2):

        return num1 + num2

    def sub(num1,num2):
        return num1 - num2

    def mul(num1,num2):
        return num1 * num2
    
    def div(num1,num2):
        return num1 / num2
