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

#define ll long long int
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll a, b, s;
  map<ll, vector<pair<ll, ll>>> mp;
  cin >> a >> b >> s;
  for (ll i = 1; i <= s; i++) {
    for (ll x = 1; x * x <= i; x++) {
      if (i % x == 0) {
        mp[i].push_back({x, i / x});
        if (x != i / x) {
          mp[i].push_back({i / x, x});
        }
      }
    }
  }
  ll ans = 0;
  for (ll i = 0; i <= a; i++) {
    for (ll j = 0; j <= b; j++) {
      for (ll x = 1; x <= s; x++) {
        for (auto p : mp[x]) {
          if (i + p.first <= a && j + p.second <= b) {
            ans++;
          }
        }
      }
    }
  }
  cout << ans << endl;
  return 0;
}