/**
 *    author:   K.R.Surrya  
 *    created:  02.06.2020 17:44:49
**/
#include<bits/stdc++.h>
using namespace std; 
using lint  =                           long long int;
using pint  =                           pair<int, int>;
using plint =                           pair<lint, lint>;
#define vli                             vector<lint>
#define pb                              push_back
#define ALL(x)                          begin(x),end(x)
#define inf                             (1LL<63)-1
#define MOD                             1000000007
#define SZ(x)                           ((lint)(x).size())
#define                                 FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define                                 IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define                                 REP(i, n) FOR(i,0,n)
#define                                 IREP(i, n) IFOR(i,0,n)
#define                                 f_ip   ios_base::sync_with_stdio(false); cin.tie(NULL);
#define                                 debug(x) cerr << #x << " " << (x) << endl
struct fast_ios                         { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
template<typename T>                    istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T>                    bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T>                    bool chmin(T &m, const T q) { if (q < m) {m = q; return true;} else return false; }
mt19937                                 rng(chrono::steady_clock::now().time_since_epoch().count());
lint pow_mod(lint base,lint expo) { 
   lint ret = 1;
   for(;expo;) { 
      if(expo&1)  ret = (ret*base)%MOD; 

      expo = (expo>>1);
      base = (base*base)%MOD;
   }
   return ret;
}
#define sim template <class c
#define ris return *this
#define dor > deb &operator<<
#define eni(x)                                                                  \
    sim > typename enable_if<sizeof dud<c>(0) x 1, deb &>::type operator<<(c i) \
    {
sim > struct rge
{
    c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct deb
{
#ifdef LOCAL
    ~deb()
    {
        cerr << endl;
    }
    eni(!=) cerr << boolalpha << i;
    ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d)
{
    ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d)
{
    *this << "[";
    for (auto it = d.b; it != d.e; ++it)
        *this << ", " + 2 * (it == d.b) << *it;
    ris << "]";
}
#else
    sim dor(const c &)
    {
        ris;
    }
#endif
}
;
#define simsim(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
// -DLOCAL

double pi=acos(-1);
void solve() {
      double a,b;
     cin >> a >> b;
      double h,m;
      cin >> h >> m;

    
    /* triangle property :-
    //   b*=-1; //1/
      double two=m*6.00;
    //   two+=180.00;
    //   if(two>360.00) two-=360.00;//2/
      double add=(1.00/60.00)*m*5*6; // 1 h ==> 1*5*6 degrees; 
      double one=(h*5*6)+add;

      double diff=(max(one,two)-min(one,two));
      //diff=360.00-diff; //doesn't affect the final result ;;;
     
     deb() << simsim(add);
     deb() << simsim(diff) simsim(one) simsim(two);

     double ret= pow(a,2.0)+pow(b,2.0) -(2.0)*a*b*(cos((pi/180.00)*diff)); //vector sum , with angle between the vectors reversed;;; Parallelogram formula ;;;
     cout << sqrt(ret) ;
     deb() << simsim(diff) simsim(cos((pi/180.00)*diff)) simsim(pi);
     deb() << simsim(ret);
     */

    //using vector components to figure out the co-ordinates :-

    double rm=(2*pi*m/60);  //60 minutes ==> 2*pi;
    double rh=2*pi*(h*60+m)/(12*60); //12*60 minutes ==> 2*pi;
    
    double xh=cos(rh)*a;double yh=sin(rh)*a;
    double xm=cos(rm)*b;double ym=sin(rm)*b;
    cout << sqrt((xm-xh)*(xm-xh) + (ym-yh)*(ym-yh));

    deb() << simsim(xh) simsim(yh);
    deb() << simsim(xm) simsim(ym);
}

int main()
{   
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);

     auto start = chrono::high_resolution_clock::now();

     int T=1;
     //cin>>T;
     for(int tt=1;tt<=T;++tt) {
         solve();
     }
     auto end = chrono::high_resolution_clock::now();

     cerr << " Execution time : " << chrono::duration_cast<chrono::milliseconds>(end-start).count()<<"ms"<<endl;

   
    return 0;
}


Measured memory_bytes: 4156