#line 2 "header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) { if ((a) < (b)) (a) = (b); }
template <class T> inline void chmin(T &a, const T &b) { if ((a) > (b)) (a) = (b); }
template <typename X, typename T> auto make_table(X x, T a) { return vector<T>(x, a); }
template <typename X, typename Y, typename Z, typename... Zs> auto make_table(X x, Y y, Z z, Zs... zs) { auto cont = make_table(y, z, zs...); return vector<decltype(cont)>(x, cont); }

#define divceil(a, b) ((a) + (b)-1) / (b)
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x) sort(all(x)); x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T>
using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() { assert(cin.eof() == 0); int tmp; cin >> tmp; assert(cin.eof() == 1); }

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "solve.cpp"
template<class T=ll> using vec = vector<T>;
struct Fast { Fast() { std::cin.tie(0); ios::sync_with_stdio(false); } } fast;


long double rad(long double d){
    return d * M_PI / 180.0;
}

template<class T=ll>/*{{{*/
struct P2 {
    T x, y;
    P2(T _x, T _y) : x(_x), y(_y) {}
    P2() {
        x = 0;
        y = 0;
    }
    bool operator<(const P2 &r) const {
        return (x != r.x ? x < r.x : y < r.y);
    }
    bool operator>(const P2 &r) const {
        return (x != r.x ? x > r.x : y > r.y);
    }
    bool operator==(const P2 &r) const { return (x == r.x && y == r.y); }

    friend ostream &operator<<(ostream &stream, P2 p) {
        stream << "(" << p.x << "," << p.y << ")";
        return stream;
    }

    P2 operator-() const {  // 単項演算子
        return P2(-x, -y);
    }

    P2& operator+=(const P2<T>& r){
        x += r.x;
        y += r.y;
        return *this;
    }
    P2& operator-=(const P2<T>& r){
        x -= r.x;
        y -= r.y;
        return *this;
    }
    P2& operator+=(const T& r){
        x += r;
        y += r;
        return *this;
    }
    P2& operator-=(const T& r){
        x -= r;
        y -= r;
        return *this;
    }
    P2& operator*=(const P2<T>& r){
        x *= r.x;
        y *= r.y;
        return *this;
    }
    P2& operator/=(const P2<T>& r){
        x /= r.x;
        y /= r.y;
        return *this;
    }
    P2& operator*=(const T& r){
        x *= r;
        y *= r;
        return *this;
    }
    P2& operator/=(const T& r){
        x /= r;
        y /= r;
        return *this;
    }

    template<class U>
    P2 operator+(const U& r) const {
        P2 res(*this);
        return res += r;
    }
    template<class U>
    P2 operator-(const U& r) const {
        P2 res(*this);
        return res -= r;
    }

    template<class U>
    P2 operator*(const U& r) const {
        P2 res(*this);
        return res *= r;
    }
    template<class U>
    P2 operator/(const U& r) const {
        P2 res(*this);
        return res /= r;
    }


    bool in(T a, T b, T c, T d) {  // x in [a, b) && y in [c, d)
        if (a <= x && x < b && c <= y && y < d) return true;
        else return false;
    }

};/*}}}*/
using P = P2<ll>;

template<class T>
double dist(const T& p, const T& q){
    return sqrt((p.x - q.x) * (p.x - q.x) + (p.y - q.y) * (p.y - q.y));
}

int solve() {
    ld a,b,h,m;cin>>a>>b>>h>>m;

    ld s = 6 * m;
    ld l = 30.0 * (h + m/60);

    P2<ld> p(a * cos(rad(l)), a * sin(rad(l)));
    P2<ld> q(b * cos(rad(s)), b * sin(rad(s)));

    printf("%.12f\n", dist(p, q));

    return 0; 
}


int main(){/*{{{*/
    solve();
    check_input();
    return 0;
}/*}}}*/


Measured memory_bytes: 4204