#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001
long long get(long long n){
	return n * (n+1) / 2;
}
long long get(long long l,long long r){
	return get(r) - get(l-1);
}

int main() {	
	
	long long A,B,S;
	cin>>A>>B>>S;
	long long ans = 0;
	for(long long i=1;i<=S;i++){
		long long l = 1;
		long long r = S/i;
		long long x = A-i+1;
		if(x<=0)continue;
		
		long long y = get(max(1LL,B-r+1),B);
		ans += x*y;
	}
	cout<<ans<<endl;
	
    return 0;
}