/* -*- coding: utf-8 -*-
 *
 * 2043.cc:  No.2043 Ohuton and Makura - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

inline ll sigma(int n) { return (ll)n * (n + 1) / 2; }

/* main */

int main() {
  int a, b, s;
  scanf("%d%d%d", &a, &b, &s);

  ll sum = 0;
  int maxp = min(a, s);
  for (int p = 1; p <= maxp; p++) {
    int q = min(s / p, b);
    if (q > 0)
      sum += (a - p + 1) * (sigma(b) - sigma(b - q));
  }

  printf("%lld\n", sum);
  return 0;
}