#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>
#include <iomanip>
#include <stack>
#include <queue>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <fstream>
#include <chrono>
#include <random>
#include <bitset>
//#include <atcoder/all>
#include <sstream>
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((int)(x).size())
#define pb push_back
using ll = long long;
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
ll gcd(ll a, ll b) {return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) {return a/gcd(a,b)*b;}

ll f(ll x){
  return x*(x+1)/2;
}

int main(){
  ll A,B,S; cin >> A >> B >> S;
  ll ans = 0;
  for(ll h=1;h<=min(A,S);h++){
    ll ok=1,ng=min(B,S)+1;
    while(abs(ok-ng)>1){
      ll mid = (ok+ng)/2;
      if(h*mid<=S) ok=mid;
      else ng=mid;
    }
    ans += (A-h+1)*(f(B)-f(B-ok));
  }
  cout << ans << endl;
  return 0;
}