import java.io.*;
import java.util.*;

class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader bu=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb=new StringBuilder();
        String s[]=bu.readLine().split(" ");
        int n=Integer.parseInt(s[0]),m=Integer.parseInt(s[1]),area=Integer.parseInt(s[2]);
        long ans=0;
        for(int i=1;i<=area;i++)
        {
            long hor=n+1-i; //number of rows where we can place this
            if(hor<=0) break;
            //we need to multiply this with m+1-1 + m+1-2 + m+1-3 + ...+ m+1-breadth (consider only +ve values)
            //we need to make sure the cells covd is less area, so consider breadth
            int breadth=area/i, right=Math.max(0,m-breadth);
            long vsum=sum(m)-sum(right);
            ans+=hor*vsum;
        }
        System.out.println(ans);
    }

    static long sum(int n)
    {
        return 1l*n*(n+1)/2;
    }
}