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

long long a, b, s, m;

int main() {
	cin >> a >> b >> s;

	for (long long i = 1; i <= a; i++) {
		if (s / i > b) {
			m += (a - i + 1) * (b + 1) * b / 2;
		}
		else {
			m += (a - i + 1) * (2 * b + 1 - s / i) * (s / i) / 2;
		}
	}

	cout << m << endl;
}