#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>

// increment
#define rep_n(_1, _2, _3, NAME, ...) NAME
#define rep_2(i, n) for (int(i) = 0; (i) < (int)(n); ++(i))
#define rep_3(i, initial, n) for (int(i) = (int)(initial); (i) < (int)(n); ++(i))
#define rep(...) rep_n(__VA_ARGS__, rep_3, rep_2, rep_1)(__VA_ARGS__)
// decrement
#define rep_r_n(_1, _2, _3, NAME, ...) NAME
#define rep_r_2(i, n) for (int(i) = (int)(n); (i) > 0; (i)--)
#define rep_r_3(i, initial, n) for (int(i) = (int)(initial); (i) > (int)(n); (i)--)
#define rep_r(...) rep_r_n(__VA_ARGS__, rep_r_3, rep_r_2)(__VA_ARGS__)
// define type definition
using namespace std;
typedef long long ll;
using mpint = boost::multiprecision::cpp_int; // 多倍長整数（任意精度）
typedef pair<int, int> P;

// define construct variable
const double EPS = numeric_limits<double>::epsilon();
// 10^9 + 7
const ll MOD = ll(1e9) + 7;
const ll INF = ll(1e10);
const string ALPHABET = "abcdefghijklmnopqrstuvwxyz";

// define methods
// 最大公約数
ll gcd(const ll a, const ll b) { return b ? gcd(b, a % b) : a; }
// 最小公倍数
ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }
// char -> int
int ctoi(char c) { return (int)(c - '0'); }
// 素因数分解
vector<pair<ll, ll>> prime_factorize(ll n)
{
	vector<pair<ll, ll>> p;
	for (ll i = 2; i * i <= n; i++)
	{
		if ((n % i) != 0)
			continue;
		p.push_back(make_pair(i, 0));
		while ((n % i) == 0)
		{
			n /= i;
			p[i].second += 1;
		}
		p.push_back(make_pair(n, 0));
	}

	if (n != 1)
		p.push_back(make_pair(n, 1));
	return p;
}
// 組み合わせの整合性を保つ（後ほど解析する）
ll modinv(ll a)
{
	ll b = MOD, u = 1, v = 0;
	while (b)
	{
		ll t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= MOD;
	if (u < 0)
	{
		u += MOD;
	}
	return u;
}
// 順列
ll permutation(const ll n, const ll m)
{
	ll result = 1;
	for (ll i = n; i > n - m; i--)
	{
		result = (result * i) % MOD;
	}
	return result;
}

// 繰り返し n 乗法
ll repeat_square(const ll n, const ll x)
{
	if (x == 0)
		return 1;
	ll res = repeat_square(n, x / 2);
	res = res * res % MOD;
	if ((x % 2) == 1)
		res = res * n % MOD;
	return res;
}
// 組み合わせ
ll combination(const ll n, const ll a)
{
	ll x = 1, y = 1;
	for (ll i = 0; i < a; i++)
	{
		x = x * (n - i) % MOD;
		y = y * (i + 1) % MOD;
	}
	return x * repeat_square(y, MOD - 2) % MOD;
}

int result = 0;

void dfs(int N, int M, int Q, vector<int> A, map<int, vector<int>> m)
{
	if (A.size() == N + 1)
	{ // 最初に入っている [1] は除いた数列で判定するため
		int temp = 0;
		rep(i, Q)
		{
			int a = m[i][0];
			int b = m[i][1];
			int c = m[i][2];
			int d = m[i][3];
			if ((A[b] - A[a]) == c)
				temp += d; // Aは 1番目から参照しているため、添字は -1 しなくて良い
		}

		if (temp > result)
			result = temp;
		return;
	}
	A.push_back(A.back()); // 直前の数を push（A1 <= A2 <= A3 ... An のため）
	while (A.back() <= M)
	{
		dfs(N, M, Q, A, m);
		A.back()++;
	}
}

int main()
{
	int A, B, H, M;
	cin >> A >> B >> H >> M;
	double result = 0;

  const long double PI = acos(-1);
	double h = H * 30 + M * (double)360 / (12 * 60); // 360 / 12 * 60
	double m = M * 6;
	double x = abs(h - m) ; // 度数×(π/180)

	result = sqrt(A*A + B*B - 2 * A * B * cos(x * (PI/180)));

	cout << fixed << setprecision(20) << result << endl;

	return 0;
}


Measured memory_bytes: 4140