/** * author: otera **/ #include using namespace std; #define int long long using ll = long long; using ld = long double; using ull = unsigned long long; using int128_t = __int128_t; #define repa(i, n) for(int i = 0; i < n; ++ i) #define repb(i, a, b) for(int i = a; i < b; ++ i) #define repc(i, a, b, c) for(int i = a; i < b; i += c) #define overload4(a, b, c, d, e, ...) e #define overload3(a, b, c, d, ...) d #define rep(...) overload4(__VA_ARGS__, repc, repb, repa)(__VA_ARGS__) #define rep1a(i, n) for(int i = 0; i <= n; ++ i) #define rep1b(i, a, b) for(int i = a; i <= b; ++ i) #define rep1c(i, a, b, c) for(int i = a; i <= b; i += c) #define rep1(...) overload4(__VA_ARGS__, rep1c, rep1b, rep1a)(__VA_ARGS__) #define rev_repa(i, n) for(int i=n-1;i>=0;i--) #define rev_repb(i, a, b) assert(a > b);for(int i=a;i>b;i--) #define rev_rep(...) overload3(__VA_ARGS__, rev_repb, rev_repa)(__VA_ARGS__) #define rev_rep1a(i, n) for(int i=n;i>=1;i--) #define rev_rep1b(i, a, b) assert(a >= b);for(int i=a;i>=b;i--) #define rev_rep1(...) overload3(__VA_ARGS__, rev_rep1b, rev_rep1a)(__VA_ARGS__) typedef pair P; typedef pair LP; #define pb push_back #define pf push_front #define ppb pop_back #define ppf pop_front #define eb emplace_back #define fr first #define sc second #define all(c) c.begin(),c.end() #define rall(c) c.rbegin(), c.rend() #define lb(c, x) distance((c).begin(), lower_bound(all(c), (x))) #define ub(c, x) distance((c).begin(), upper_bound(all(c), (x))) #define Sort(a) sort(all(a)) #define Rev(a) reverse(all(a)) #define Uniq(a) sort(all(a));a.erase(unique(all(a)),end(a)) #define si(c) (int)(c).size() inline ll popcnt(ull a){ return __builtin_popcountll(a); } #define kth_bit(x, k) ((x>>k)&1) #define unless(A) if(!(A)) ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; } ll intpow(ll a, ll b, ll m) {ll ans = 1; while(b){ if(b & 1) (ans *= a) %= m; (a *= a) %= m; b /= 2; } return ans; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } #define INT(...) int __VA_ARGS__;in(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;in(__VA_ARGS__) #define ULL(...) ull __VA_ARGS__;in(__VA_ARGS__) #define STR(...) string __VA_ARGS__;in(__VA_ARGS__) #define CHR(...) char __VA_ARGS__;in(__VA_ARGS__) #define DBL(...) double __VA_ARGS__;in(__VA_ARGS__) #define LD(...) ld __VA_ARGS__;in(__VA_ARGS__) #define vec(type,name,...) vectorname(__VA_ARGS__) #define VEC(type,name,size) vectorname(size);in(name) #define vv(type,name,h,...) vector>name(h,vector(__VA_ARGS__)) #define VV(type,name,h,w) vector>name(h,vector(w));in(name) #define vvv(type,name,h,w,...) vector>>name(h,vector>(w,vector(__VA_ARGS__))) template using vc = vector; template using vvc = vector>; template using vvvc = vector>; template using vvvvc = vector>; template using pq = priority_queue; template using pqg = priority_queue, greater>; template using umap = unordered_map; template void scan(T& a){ cin >> a; } template void scan(vector& a){ for(auto&& i : a) scan(i); } void in(){} template void in(Head& head, Tail&... tail){ scan(head); in(tail...); } void print(){ cout << ' '; } template void print(const T& a){ cout << a; } template void print(const vector& a){ if(a.empty()) return; print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ cout << ' '; print(*i); } } int out(){ cout << '\n'; return 0; } template int out(const T& t){ print(t); cout << '\n'; return 0; } template int out(const Head& head, const Tail&... tail){ print(head); cout << ' '; out(tail...); return 0; } #define CHOOSE(a) CHOOSE2 a #define CHOOSE2(a0,a1,a2,a3,a4,x,...) x #define debug_1(x1) cout<<#x1<<": "< l(n); l[0] = (ld)h[0]; rep(i, n - 1) { l[i + 1] = (ld)h[i + 1] - (ld)h[i]; } VEC(int, a, n); ld ans = (ld)x * (ld)a[0]; rep(i, 1, n) { auto f = [&](ld theta) -> ld { ld ret = l[0] / cos(theta) * (ld)a[0]; ld si = sin(theta); ld cur = l[0] * tan(theta); for(int j = 0; j < i - 1; ++ j) { si = si / (ld)a[j + 1] * (ld)a[j]; ld co = sqrt(max((ld)0.0, (ld)1.0 - si * si)); ld ta = si / co; cur += l[j] * ta; ret += l[j + 1] / co * (ld)a[j + 1]; } if(cur > (ld)x / 2.0 + eps) return INF; ret += ((ld)x / 2.0 - cur) * a[i]; return ret; }; ld l = 0.0, r = pi / 2.0; rep(_, 100) { ld ml = (l * 2.0 + r) / 3.0; ld mr = (l + r * 2.0) / 3.0; if(f(ml) < f(mr)) r = mr; else l = ml; } chmin(ans, f(l) * 2.0); if(a[i] == 0) break; } out(ans); } signed main() { int testcase = 1; in(testcase); while(testcase--) solve(); return 0; }