#include "bits/stdc++.h"
using namespace std;
using     ll=long long;     using   dd=double;     
using    vll=vector<   ll>; using  vdd=vector< dd>;
using   vvll=vector<  vll>; using vvdd=vector<vdd>;
using  vvvll=vector< vvll>;
using vvvvll=vector<vvvll>;
using   pll=pair<ll,ll>;  using   tll=tuple<ll,ll,ll>; using   qll=tuple<ll,ll,ll,ll>;
using  vpll=vector< pll>; using  vtll=vector< tll>;    using  vqll=vector< qll>;
using vvpll=vector<vpll>; using vvtll=vector<vtll>;    using vvqll=vector<vqll>;
constexpr ll INF = 1LL << 60;
struct Fast{ Fast(){ cin.tie(0); ios::sync_with_stdio(false); cout<<fixed<<setprecision(numeric_limits<double>::max_digits10); } } fast;
#define REPS(i, S, E) for (ll i = (S); i <= (E); i++)
#define REP(i, N) REPS(i, 0, (N)-1)
#define DEPS(i, S, E) for (ll i = (E); i >= (S); i--)
#define DEP(i, N) DEPS(i, 0, (N)-1)
#define rep(i, S, E)  for (ll i = (S); i <= (E); i++)
#define dep(i, E, S)  for (ll i = (E); i >= (S); i--)
#define each(e, v) for (auto&& e : v)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
template<class T> inline T MaxE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmax(m,v[i]); return m; }
template<class T> inline T MinE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmin(m,v[i]); return m; }
template<class T> inline T MaxE(vector<T> &v) { return MaxE(v,0,(ll)v.size()-1); }
template<class T> inline T MinE(vector<T> &v) { return MinE(v,0,(ll)v.size()-1); }
template<class T> inline T Sum(vector<T> &v,ll S,ll E){ T s=T(); rep(i,S,E)s+=v[i]; return s; }
template<class T> inline T Sum(vector<T> &v) { return Sum(v,0,v.size()-1); }
template<class T> inline ll sz(T &v){ return (ll)v.size(); }
inline ll CEIL(ll a,ll b){ return (a<0) ? -(-a/b) : (a+b-1)/b; }
inline ll FLOOR(ll a,ll b){ return -CEIL(-a,b); }



#if 0
#include <atcoder/all>
using namespace atcoder;
#endif


template<class T,class S> inline ll RightNumOf(vector<T> &v,S x){
	return (ll)v.size() - (lower_bound(ALL(v),x) - v.begin());
}
/*  x以右(以上)の個数を得る。vが昇順の時のみ。
ll nm = RightNumOf(v, x);
*/



void solve()
{
	ll n,m,c;  cin >> n >> m >> c;
	vector<ll> a(n);  rep(i,0,n-1){ ll a_; cin>>a_; a[i]=a_; }
	vector<ll> b(m);  rep(i,0,m-1){ ll b_; cin>>b_; b[i]=b_; }

	sort(ALL(a));
	sort(ALL(b));
	
	ll cnt=0;
	each(e,a){
		ll bb=CEIL(c+1,e);
		ll nm=RightNumOf(b,bb);
		cnt+=nm;
	}
	dd ans=cnt/(dd)(n*m);
	cout << ans << '\n';

}

int main(){
#if 1
	solve();
	//cin2solve();
	//generand();
#else
	ll t;  cin >> t;
	rep(i, 0, t-1){
		solve();
		//cin2solve();
	}
#endif
	return 0;
}