def main():
    print('==Exercise 3==')
    flag=True
    while flag:
        a = input("pls input first side length:")
        try: 
            a = float(a)
            flag=False
        except :
            print("pls input a float!")
    flag=True
    while flag:
        b = input("pls input another side length:")
        try: 
            b = float(b)
            flag=False
        except :
            print("pls input a float!")

    print(f"The lenth of the hypotenuse= {sum([i**2 for i in [a,b]])**0.5}")

    print('==End Of Ex3==')
    return 0

if __name__ == '__main__':
    main()