#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
#endif

#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m - 1; i >= n; --i)
#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v, n) reverse(v, v + n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout << (x) << '\n'
#define pe(x) cout << (x) << " "
#define DEBUG(x) cout << #x << ": " << x << endl
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
#define int long long
//#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << ((i == v.size() - 1) ? "\n" : " ")
template <typename T1, typename T2> inline void chmin(T1& a, T2 b) {
	if (a > b) a = b;
}
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) {
	if (a < b) a = b;
}
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef array<int, 3> arr3;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 998244353;
constexpr int MAX = 5050;
const double pi = acos(-1);
// constexpr double EPS = 1e-10;
constexpr ll INF = 1e16;
void yes(bool c) {
	if (c)
		print("Yes");
	else
		print("No");
};
typedef complex<double> point;
istream &operator>>(istream &is, point &p) {
	double a, b;
	is >> a >> b;
	p = point(a, b);
	return is;
}
const double EPS = 1e-10;


point operator*(const point &p, const double &d) {
	return point(real(p) * d, imag(p) * d);
}
namespace std {
	bool operator<(const point &a, const point &b) {
		return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
	}
}  // namespace std

   //直線or線分
struct Line : public vector<point> {
	Line(const point &a, const point &b) {
		push_back(a);
		push_back(b);
	}
};
typedef vector<Line> Lines;

point direction(const point &p) {  //同じ向きの単位ベクトル
	return p / abs(p);
}
point orthogonal(const point &p) {  //法線ベクトル
	return point(-imag(p), real(p));
}
double cross(const point &a, const point &b) {
	return real(a) * imag(b) - imag(a) * real(b);
}
double dot(const point &a, const point &b) {
	return real(a) * real(b) + imag(a) * imag(b);
}
int ccw(point a, point b, point c) {
	b = b - a;
	c = c - a;
	if (cross(b, c) > EPS) return +1;   // counter clockwise
	if (cross(b, c) < -EPS) return -1;  // clockwise
	if (dot(b, c) < -EPS) return +2;    // c--a--b on line
	if (norm(b) < norm(c)) return -2;   // a--b--c on line
	return 0;
}
void solve() {
	double A, B, H, M; cin >> A >> B >> H >> M;
	double t1 = 2 * pi*(H*60+M) / 12.0/60.0;
	double t2 = 2 * pi*M / 60.0;
	point p1(A, 0), p2(B, 0);
	//cerr << t1 / (2 * pi) * 360 << endl;
	//cerr<< t2 / (2 * pi) * 360 << endl;
	//t1 = 0, t2 = pi;
	point q1(cos(t1), sin(t1)), q2(cos(t2), sin(t2));
	p1 *= q1;
	p2 *= q2;
	cout << fixed << setprecision(15) << abs(p1 - p2) << endl;
}
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	// int q;
	// cin >> q;
	// while (q--)
	solve();
}


Measured memory_bytes: 4156