#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
const long long mod = 1e9 + 7;
const int alphabet = 26;
const int inf = INT_MAX;
const long long linf = 1e18 + 9;
namespace util {
inline long long cnm(char ch) { return (ch - '0'); }
inline long long cap(char ch) { return (ch - 'a'); }
inline void instr(string& s, long long& n) {
  cin >> s;
  n = s.length();
}
inline void instr(string& s) { cin >> s; }
template <typename T>
T gcd(T a, T b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
template <typename T>
bool min(T a, T b, T c) {
  return std::min(a, std::min(b, c));
}
}  // namespace util
using namespace util;
void solve(int tc) {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long i, j, k, m, n;
  long long a, b, h;
  cin >> a >> b >> h >> m;
  long long hangle = h * 30;
  long long mangle = m * 6;
  long double angle = abs(hangle - mangle);
  cout << "angle(before): " << angle << "\n";
  if (angle > 180) angle = 360 - angle;
  cout << "angle(after): " << angle << "\n";
  long double csqr = 1.0 * a * a + 1.0 * b * b -
                     1.0 * 2 * a * b * cos((1.0 * angle * acos(-1)) / 180.0);
  printf("%.9lf", csqr);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  int i = 1;
  while (i <= t) {
    solve(i);
    i++;
  }
  return 0;
}
