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

int main() {
    int A,B,S;
    cin >> A >> B >> S;
    long long ans = 0;
    for(int i = 1; i <= S; i++) {
        if(i <= A) {
            int j = min(S/i,B);
            long long tmp = 1ll*(B+B-j+1)*j/2;
            ans += 1ll*(A-i+1)*tmp;
        }
    }
    cout << ans << endl;
}