#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; --i)

int main() {
    int a, b, s;
    cin >> a >> b >> s;
    vector<ll> sa(a + 1);
    rep(i, a) sa[i + 1] = sa[i] + a - i;
    ll ret = 0;
    for (int j = 1; j <= b; j++) {
        ret += sa[min(a, s / j)] * (b - j + 1);
    }
    cout << ret << endl;
    return 0;
}