import sys,random,bisect
from collections import deque,defaultdict,Counter
from heapq import heapify,heappop,heappush
from itertools import cycle, permutations
from math import log,gcd

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

A,B,S = mi()

res = 0
for h in range(1,S+1):
    w_max = min(S//h,B)
    if h <= A:
        #res += (A-h+1) * (B-w+1)
        res += (A-h+1) * (w_max * (B+1) - w_max * (w_max+1)//2)

print(res)