A, B, S = map(int, input().split())
spf = [-1 for _ in range(S + 5)]
spf[0] = 0; spf[1] = 1
for i in range(2, S + 1):
    if spf[i] == -1:
        for j in range(i, S + 1, i):
            if spf[j] == -1:
                spf[j] = i
ans = 0
for s in range(1, S + 1):
    r = s
    div = set()
    div.add(1)
    while s != 1:
        p = spf[s]
        t = set()
        for px in div:
            t.add(px * p)
        div = div | t
        s //= p
    for x in div:
        a, b = r // x, x
        if a <= A and b <= B:
            ans += (A - a + 1) * (B - b + 1)

print(ans)