#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    long long ans = 0;
    int a, b, s; cin >> a >> b >> s;
    for (int hei = 1; hei <= min(a, s); hei++) {
        long long wid = min(b, s / hei);
        // wid * b - wid * (wid - 1) / 2
        // b -> b - wid + 1
        ans += 1LL * (a - hei + 1) * (wid * b - wid * (wid - 1) / 2);
    }
    cout << ans;
}