a, b, s = map(int, input().split())
d = [0] * (b + 1)
for h in range(1, b + 1):
    d[h] = d[h - 1] + b - h + 1
ans = 0
for w in range(1, a + 1):
    ans += (a - w + 1) * d[min(s // w, b)]
print(ans)