#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 1e5+1, oo = 1e9;
int main() {
    ll A,B,S; cin >> A >> B >> S;
    ll ans=0;
    for(int a=1;a<=A;++a) {
        int xdif = A-a+1;
        ll mx = min(B,S/a);
        // sum from 1 to mx of:
        // B+1-i
        ans+=xdif*mx*(B + B-mx+1)/2;
    }
    cout << ans << '\n';
}