#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
#include<bitset>
#include<cassert>
#include<complex>
#include<fstream>
#include<cstdlib>
#include<functional>
using namespace std;
typedef long long ll;
const int mod=998244353;
const int dx[]={1,0,0,-1},dy[]={0,1,-1,0};
int main(){
	int a,b,s;
	cin>>a>>b>>s;
	ll ans=0;
	for(int i=1;i<=a;i++){
		int v=b-min(s/i,b);
		ans+=(a-i+1)*(b*(b+1ll)/2-v*(v+1ll)/2);
	}
	cout<<ans<<endl;
}