#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

int main() {
  ll a, b, s; cin >> a >> b >> s;
  ll ans = 0;
  for (ll x = 1; x <= a; x++) {
    for (ll y = 1; y <= b; y++) {
      if (x * y > s) break;
        ans += (a - x + 1) * (b - y + 1);
    }
  }
  cout << ans << endl;
  return 0;
}