class Steel():
    def __init__(self,steeltype,thickness,density,a,b=0):
        self.steeltype = steeltype
        self.thickness = thickness
        self.density = density
        self.a = a
        self.b = b

    def S(self):
        if self.steeltype==1:
            s=a*a
        if self.steeltype==2:
            s=a*b
        if self.steeltype==3:
            s=(a*b)/2
        print(s)

    def weight(self):
        weigh=(S()*0.001)*self.thickness*self.density

    def INFO():
        print(self.steeltype,self.thickness,self.density,S(),weight())

d=Steel(1,2,7800,4)
d.S()