#include<iostream>
using namespace std;
int A,B,S;
int main()
{
	cin>>A>>B>>S;
	long ans=0;
	for(int x=1;x<=S&&x<=A;x++)
	{
		long up=min(B,S/x);
		ans+=(long)(A-x+1)*((B+1)*up-up*(up+1)/2);
	}
	cout<<ans<<endl;
}