#include using namespace std; #pragma region atcoder /*#include using namespace atcoder;*/ //using mint = modint998244353; //using mint = modint1000000007; #pragma endregion #pragma region macros using ll = long long; using pii = pair; using pll = pair; using vi = vector; using vs = vector; using vl = vector; using vb = vector; using vvi = vector>; using vvl = vector>; #define rep(i, n) for(int i = 0; i < n; i++) #define REP(i, a, b) for(int i = a; i < b; i++) #define rrep(i, n) for(int i = n - 1; i >= 0; i--) #define RREP(i, a, b) for(int i = b - 1; i >= a; i--) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() #define sz(x) ((int)(x).size()) #define pb push_back #define lb lower_bound #define ub upper_bound #define fi first #define se second #pragma endregion #pragma region debug for var, v, vv #define debug(var) do{std::cout << #var << " : ";view(var);}while(0) template void view(T e){std::cout << e << std::endl;} template void view(const std::vector& v){for(const auto& e : v){ std::cout << e << " "; } std::cout << std::endl;} template void view(const std::vector >& vv){cout << endl;int cnt = 0;for(const auto& v : vv){cout << cnt << "th : "; view(v); cnt++;} cout << endl;} #pragma endregion #pragma region int128 std::ostream &operator<<(std::ostream &dest, __int128_t value) { std::ostream::sentry s(dest); if (s) { __uint128_t tmp = value < 0 ? -value : value; char buffer[128]; char *d = std::end(buffer); do { --d; *d = "0123456789"[tmp % 10]; tmp /= 10; } while (tmp != 0); if (value < 0) { --d; *d = '-'; } int len = std::end(buffer) - d; if (dest.rdbuf()->sputn(d, len) != len) { dest.setstate(std::ios_base::badbit); } } return dest; } #pragma endregion const ll mod = 1000000007; const int inf = 1001001001; const ll INF = 1001001001001001001; int dx[4]={1,0,-1,0}; int dy[4]={0,1,0,-1}; templatebool chmax(T &a, const T b) { if (abool chmin(T &a, const T b) { if (b0&&a%b); } // 20 / 3 == 7 ll rddiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // -20 / 3 == -7 ll power(ll a, ll p){ll ret = 1; while(p){if(p & 1){ret = ret * a;} a = a * a; p >>= 1;} return ret;} ll modpow(ll a, ll p){ll ret = 1; while(p){if(p & 1){ret = ret * a % mod;} a = a * a % mod; p >>= 1;} return ret;} /*--------------------------------------------------------------------------------------------------------------------------------*/ int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15); ll n, m, c; cin >> n >> m >> c; vl a(n), b(m); rep(i,n) cin >> a[i]; rep(i,m) cin >> b[i]; sort(all(b)); ll cnt = 0; rep(i,n){ auto it = lower_bound(all(b), rudiv(c + 1, a[i])); cnt += b.end() - it; } cout << (double)cnt/(n*m) << endl; } /* * review you code when you get WA (typo? index?) * int overflow, array bounds * special cases (n=1?) */