#ifdef ONLINE_JUDGE #pragma GCC target("avx2,avx") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #endif #include using namespace std; using ll = long long; using ull = unsigned long long; using i128 = __int128_t; using pii = pair; using pll = pair; #define rep(i, n) for (int i = 0; i < (n); i++) #define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--) #define all(x) (x).begin(), (x).end() constexpr char ln = '\n'; istream& operator>>(istream& is, __int128_t& x) { x = 0; string s; is >> s; int n = int(s.size()), it = 0; if (s[0] == '-') it++; for (; it < n; it++) x = (x * 10 + s[it] - '0'); if (s[0] == '-') x = -x; return is; } ostream& operator<<(ostream& os, __int128_t x) { if (x == 0) return os << 0; if (x < 0) os << '-', x = -x; deque deq; while (x) deq.emplace_front(x % 10), x /= 10; for (int e : deq) os << e; return os; } template ostream& operator<<(ostream& os, const pair& p) { return os << "(" << p.first << ", " << p.second << ")"; } template ostream& operator<<(ostream& os, const vector& v) { os << "{"; for (int i = 0; i < int(v.size()); i++) { if (i) os << ", "; os << v[i]; } return os << "}"; } template inline int SZ(Container& v) { return int(v.size()); } template inline void UNIQUE(vector& v) { v.erase(unique(v.begin(), v.end()), v.end()); } template inline bool chmax(T1& a, T2 b) { if (a < b) {a = b; return true ;} return false ;} template inline bool chmin(T1& a, T2 b) { if (a > b) {a = b; return true ;} return false ;} inline int topbit(int x) { return x == 0 ? -1 : 31 - __builtin_clz(x); } inline int topbit(long long x) { return x == 0 ? -1 : 63 - __builtin_clzll(x); } inline int botbit(int x) { return x == 0 ? 32 : __builtin_ctz(x); } inline int botbit(long long x) { return x == 0 ? 64 : __builtin_ctzll(x); } inline int popcount(int x) { return __builtin_popcount(x); } inline int popcount(long long x) { return __builtin_popcountll(x); } inline int kthbit(long long x, int k) { return (x>>k) & 1; } inline constexpr long long TEN(int x) { return x == 0 ? 1 : TEN(x-1) * 10; } inline void print() { cout << "\n"; } template inline void print(const vector& v) { for (int i = 0; i < int(v.size()); i++) { if (i) cout << " "; cout << v[i]; } print(); } template inline void print(const T& x, const Args& ... args) { cout << x << " "; print(args...); } #ifdef MINATO_LOCAL inline void debug_out() { cerr << endl; } template inline void debug_out(const T& x, const Args& ... args) { cerr << " " << x; debug_out(args...); } #define debug(...) cerr << __LINE__ << " : [" << #__VA_ARGS__ << "] =", debug_out(__VA_ARGS__) #define dump(x) cerr << __LINE__ << " : " << #x << " = " << (x) << endl #else #define debug(...) (void(0)) #define dump(x) (void(0)) #endif struct fast_ios { fast_ios() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_; //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// int main() { ll N,M,C; cin >> N >> M >> C; vector A(N),B(M); rep(i,N) cin >> A[i]; rep(i,M) cin >> B[i]; ll cnt = 0; sort(all(B)); reverse(all(B)); rep(i,N) { auto check=[&](int mid) { return A[i]*B[mid] > C; }; int ok = -1; int ng = M; while (ng-ok>1) { int mid = (ok+ng)/2; (check(mid) ? ok : ng) = mid; } cnt += ng; } cout << (double)cnt/(N*M) << ln; }