#define MOD_TYPE 2

#pragma region Macros
#include <bits/stdc++.h>
using namespace std;
/*
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using multiInt = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
*/

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

constexpr ll MOD = (MOD_TYPE == 1 ? (ll)(1e9 + 7) : 998244353);
//constexpr ll MOD = 1;
constexpr int INF = (int)1e9;
constexpr ll LINF = (ll)4e18;
constexpr ld PI = acos(-1.0);
constexpr ld EPS = 1e-11;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define MP make_pair
#define MT make_tuple
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define Yay(n) cout << ((n) ? "Yay!" : ":(") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";

inline void init_main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(30) << setiosflags(ios::fixed);
}
template <typename T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}
inline ll CEIL(ll a, ll b)
{
  return (a + b - 1) / b;
}
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val)
{
  fill((T *)array, (T *)(array + N), val);
}
#pragma endregion

struct point_t
{
  ld x, y;
  int exception = 0;

  inline void display()
  {
    if (exception == 0)
      cerr << "(" << x << ", " << y << ")\n";
    else
      cerr << "exception:" << exception << "\n";
  }

  constexpr point_t operator+(const point_t &p) const noexcept
  {
    return point_t{this->x + p.x, this->y + p.y};
  }
  constexpr point_t operator-(const point_t &p) const noexcept
  {
    return point_t{this->x - p.x, this->y - p.y};
  }
  constexpr point_t operator*(const ld &a) const noexcept
  {
    return point_t{this->x * a, this->y * a};
  }
  constexpr point_t operator/(const ld &a) const noexcept
  {
    return point_t{this->x / a, this->y / a};
  }
};

inline ld Dist(point_t &p1, point_t &p2)
{
  return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
}

//点の回転
inline point_t Rotate(point_t &p, ld theta)
{
  return point_t{p.x * cos(theta) - p.y * sin(theta), p.x * sin(theta) + p.y * cos(theta)};
}

int main()
{
  init_main();

  ld a, b, h, m;
  cin >> a >> b >> h >> m;
  ld theta1 = PI / 6.0 * h + PI / 6.0 / 60.0 * m;
  ld theta2 = PI / 30.0 * m;
  point_t p1 = {a, 0};
  point_t p2 = {b, 0};
  p1 = Rotate(p1, theta1);
  p2 = Rotate(p2, theta2);
  cout << Dist(p1, p2) << endl;


  return 0;
}

Measured memory_bytes: 4184