#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main () {
    ll a, b, s;
    cin >> a >> b >> s;
    if (a * b < s) {
        cout << 0 << endl;
        return 0;
    }
    ll ans = 0;
    for (ll p = 1; p <= min(a, s); p ++) {
        for (ll q = 1; p * q <= s; q ++) {
            if (q > b) {
                break;
            }
            ans += (a - p + 1) * (b - q + 1);
        }
    }
    cout << ans << endl;
}