#include #include using namespace std; using namespace atcoder; typedef long long ll; typedef vector vll; typedef vector vvll; typedef pair P; typedef string str; typedef vector

vp; typedef vector vs; typedef map mp; typedef set st; typedef dsu uf; typedef fenwick_tree fw; const ll mod=1e9+7; //const ll mod=998244353; const ll inf=1e18; #define rep(i,m,n) for(ll i=m;i=n;i--) #define fi first #define se second #define chmax(x,y) x=max(x,y) #define chmin(x,y) x=min(x,y) #define eb(x) emplace_back(x) #define pb(x) pop_back(x) #define all(x) x.begin(),x.end() #define allr(x) x.rbegin(),x.rend() #define lb(x,a) lower_bound(all(x),a) #define ub(x,a) upper_bound(all(x),a) #define maxe(x) max_element(all(x)) #define mine(x) min_element(all(x)) #define pc(x) __builtin_popcount(x) #define np(x) next_permutation(all(x)) void solve(){ ll n,m,c; cin >> n >> m >> c; vll a(n),b(m); rep(i,0,n) cin >> a[i]; rep(i,0,m) cin >> b[i]; sort(all(a)); sort(all(b)); long double ans=0; rep(i,0,n){ ll it=b.end()-upper_bound(all(b),c/a[i]); ans+=double(it)/double(m); } ans/=n; cout << fixed << setprecision(12) << ans << endl; } int main(){ cin.tie(nullptr); ios::sync_with_stdio(false); solve(); }