#include <bits/stdc++.h>
using namespace std;
#define int long long
#define nl "\n"
#define vi vector<int>
#define ip(x)          \
    for (auto &it : x) \
    cin >> it
#define all(x) x.begin(), x.end()

void solve()
{
    int a, b, s;
    cin >> a >> b >> s;
    int lop = min(a, s);
    int ans = 0;
    for (int i = 1; i <= lop; i++)
    {
        int x = s / i;
        if (x == 0)
            break;
        if (x > b)
            x = b;
        int area = x * (2 * b - x + 1) / 2;
        ans += (a - i + 1) * area;
    }
    cout << ans << nl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
        solve();
}