#include "bits/stdc++.h"
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// Begin Header {{{
using namespace std;

#ifndef DEBUG
#define dump(...)
#endif

#define all(x) x.begin(), x.end()
#define rep(i, b, e) for (intmax_t i = (b), i##_limit = (e); i < i##_limit; ++i)
#define reps(i, b, e) for (intmax_t i = (b), i##_limit = (e); i <= i##_limit; ++i)
#define repr(i, b, e) for (intmax_t i = (b), i##_limit = (e); i >= i##_limit; --i)
#define var(Type, ...) Type __VA_ARGS__; input(__VA_ARGS__)

constexpr size_t    operator""_zu(unsigned long long value) { return value; };
constexpr intmax_t  operator""_jd(unsigned long long value) { return value; };
constexpr uintmax_t operator""_ju(unsigned long long value) { return value; };

constexpr int INF = 0x3f3f3f3f;
constexpr intmax_t LINF = 0x3f3f3f3f3f3f3f3f_jd;

template <class T, class Compare = less<>>
using MaxHeap = priority_queue<T, vector<T>, Compare>;
template <class T, class Compare = greater<>>
using MinHeap = priority_queue<T, vector<T>, Compare>;

inline void input() {}
template <class Head, class... Tail>
inline void input(Head&& head, Tail&&... tail) {
    cin >> head;
    input(forward<Tail>(tail)...);
}

template <class T>
inline istream& operator>>(istream &is, vector<T> &vec) {
    for (auto &e: vec) {
        is >> e;
    }
    return is;
}

inline void output() { cout << "\n"; }
template <class Head, class... Tail>
inline void output(Head&& head, Tail&&... tail) {
    cout << head;
    if (sizeof...(tail)) {
        cout << " ";
    }
    output(forward<Tail>(tail)...);
}

template <class T>
inline ostream& operator<<(ostream &os, const vector<T> &vec) {
    static constexpr const char *delim[] = {" ", ""};
    for (const auto &e: vec) {
        os << e << delim[&e == &vec.back()];
    }
    return os;
}

template <class T>
inline vector<T> makeVector(const T &initValue, size_t sz) {
    return vector<T>(sz, initValue);
}

template <class T, class... Args>
inline auto makeVector(const T &initValue, size_t sz, Args... args) {
    return vector<decltype(makeVector<T>(initValue, args...))>(sz, makeVector<T>(initValue, args...));
}

template <class Func>
class FixPoint : Func {
public:
    explicit constexpr FixPoint(Func&& f) noexcept : Func(forward<Func>(f)) {}

    template <class... Args>
    constexpr decltype(auto) operator()(Args&&... args) const {
        return Func::operator()(*this, std::forward<Args>(args)...);
    }
};

template <class Func>
static inline constexpr decltype(auto) makeFixPoint(Func&& f) noexcept {
    return FixPoint<Func>{forward<Func>(f)};
}

template <class Container>
struct reverse_t {
    Container &c;
    reverse_t(Container &c) : c(c) {}
    auto begin() { return c.rbegin(); }
    auto end() { return c.rend(); }
};

template <class Container>
auto reversed(Container &c) {
    return reverse_t<Container>(c);
}

template <class T>
inline bool chmax(T &a, const T &b) noexcept {
    return b > a && (a = b, true);
}

template <class T>
inline bool chmin(T &a, const T &b) noexcept {
    return b < a && (a = b, true);
}

template <class T>
inline T diff(const T &a, const T &b) noexcept {
    return a < b ? b - a : a - b;
}
// End Header }}}

// Real {{{
const long double EPS = 1e-10;
const long double PI = acos(-1);

struct Real {
    long double x;

    Real(long double x = 0) : x(x) {}
    Real(const Real& rhs) { x = rhs.x; }

    Real operator+(const Real& rhs) const { return Real(x + rhs.x); }
    Real& operator+=(const Real& rhs) { return x += rhs.x, *this; }
    Real operator-(const Real& rhs) const { return Real(x - rhs.x); }
    Real& operator-=(const Real& rhs) { return x -= rhs.x, *this; }
    Real operator*(const Real& rhs) const { return Real(x * rhs.x); }
    Real& operator*=(const Real& rhs) { return x *= rhs.x, *this; }
    Real operator/(const Real& rhs) const { return Real(x / rhs.x); }
    Real& operator/=(const Real& rhs) { return x /= rhs.x, *this; }
    Real operator-() const { return Real(-x); }
    Real& operator++() { return ++x, *this; }
    Real& operator--() { return --x, *this; }
    Real operator++(int) { Real tmp(x); return ++x, tmp; }
    Real operator--(int) { Real tmp(x); return --x, tmp; }
    bool operator==(const Real& rhs) const { return fabs(x - rhs.x) < EPS; }
    bool operator!=(const Real& rhs) const { return !(*this == rhs); }
    bool operator<(const Real& rhs) const { return (*this == rhs) ? false : x < rhs.x; }
    bool operator>(const Real& rhs) const { return (*this == rhs) ? false : x > rhs.x; }
    bool operator<=(const Real& rhs) const { return (*this == rhs) ? true : x < rhs.x; }
    bool operator>=(const Real& rhs) const { return (*this == rhs) ? true : x > rhs.x; }
    template <class T> explicit operator T() const { return static_cast<T>(x); }

    friend istream& operator>>(istream& is, Real& rhs) {
        is >> rhs.x;
        return is;
    }
    friend ostream& operator<<(ostream& os, const Real& rhs) {
        os << rhs.x;
        return os;
    }

    friend Real pow(const Real& n, const Real& p) { return pow(n.x, p.x); }
    friend Real pow(Real n, intmax_t p) {
        Real ret = 1;
        for (; p > 0; p >>= 1) {
            if (p & 1) ret *= n;
            n *= n;
        }
        return ret;
    }
    friend Real abs(const Real& rhs) { return abs(rhs.x); }
    friend Real sin(const Real& rhs) { return sin(rhs.x); }
    friend Real cos(const Real& rhs) { return cos(rhs.x); }
    friend Real tan(const Real& rhs) { return tan(rhs.x); }
    friend Real asin(const Real& rhs) { return asin(rhs.x); }
    friend Real acos(const Real& rhs) { return acos(rhs.x); }
    friend Real atan(const Real& rhs) { return atan(rhs.x); }
    friend Real atan2(const Real& lhs, const Real& rhs) { return atan2(lhs.x, rhs.x); }
    friend Real sqrt(const Real& rhs) { return sqrt(rhs.x); }
    friend Real ceil(const Real& rhs) { return ceil(rhs.x); }
    friend Real floor(const Real& rhs) { return floor(rhs.x); }
    friend Real round(const Real& rhs) { return round(rhs.x); }
};

using real_t = Real;
real_t operator""_r(long double value) { return value; };
// }}}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.setf(ios_base::fixed);
    cout.precision(10);

    var(real_t, a, b, x);

    const real_t T = a * b;
    const real_t S = x / a;
    if (S == T) return output(0.0_r), 0;
    const real_t lim_ang1 = asin(2.0_r * S / a * a);
    const real_t lim_ang2 = atan(b * b / (2.0_r * (T - S)));

    const auto f = [&](real_t ang) -> bool {
        const real_t rad = ang / 180 * PI;
        if (S <= T / 2.0) {
            if (rad <= lim_ang1) {
                return true;
            } else {
                const real_t d = 2.0_r * S * tan(rad);
                return 0.0_r <= d && d <= b * b;
            }
        } else {
            if (rad < lim_ang2) {
                const real_t h = S / a - a * tan(rad) / 2.0;
                return h + a * tan(rad) <= b;
            } else {
                const real_t d = 2.0_r * S * tan(rad);
                return 0.0_r <= d && d <= b * b;
            }
        }
    };

    real_t ok = -1, ng = 91;
    rep(_, 0, 1000) {
        const real_t mid = (ok + ng) / 2;
        if (f(mid)) ok = mid;
        else ng = mid;
    }

    output(ok);

    return 0;
}


Measured memory_bytes: 4148