A, B, S = map(int, input().split())

max_w = min(A, S)
ans = 0

for w in range(1, max_w + 1):
    product_max = S // w
    k = min(product_max, B)
    if k < 1:
        continue
    sum_h = k * (B + 1) - k * (k + 1) // 2
    num_w = A - w + 1
    ans += num_w * sum_h

print(ans)