a, b, c = list(map(int, input().split()))#輸入三個邊長s = (a + b + c) / 2#半周長area = pow(s * (s - a) * (s - b) * (s - c), 0.5)#海龍公式求面積, 不懂的看https://lazyorangelife.com/herons-formula/ans = pow(area, 2)#面積平方print(round(ans))#四捨五入+輸出