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

int main(){

    long long a,b,s;
    cin >> a >> b >> s;

    if(a>b) swap(a,b);

    long long ans = 0;
    for(long long i=1;i<=a;i++){
        long long hight = min(b, s/i);
        ans += hight * (2*b - hight + 1) /2 * (a - i +1);
    }

    cout << ans << endl;
    return 0;
}