import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#n = int(input())
#alist = list(map(int,input().split()))
#alist = []
#s = input()
w,z,b = map(decimal.Decimal,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
print(round((w+z)*(b+1),0))