#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++){
    for (int j = 1; i * j <= S; j++){
      if (A >= i && B >= j){
        ans += (long long) (A - i + 1) * (B - j + 1);
      }
    }
  }
  cout << ans << endl;
}