#35000: python AC


1554101-0@g.puiching.edu.mo (P6A29_1300題了)


a=input()
b=a.split()
d=int(0.5*(int(b[0])+int(b[1])+int(b[2])))
e=(d*(d-int(b[0]))*(d-int(b[1]))*(d-int(b[2])))
print(e)