#include                            <iostream>
#include                            <list>
#include                            <stdio.h>
#include                            <math.h>
#include                            <string.h>
#include                            <time.h>
#include                            <stdlib.h>
#include                            <string>
#include                            <bitset>
#include                            <vector>
#include                            <set>
#include                            <map>
#include                            <queue>
#include                            <algorithm>
#include                            <sstream>
#include                            <stack>
#include                            <iomanip>
#include                            <numeric>
#include                            <unordered_map>


using namespace                     std;
#define MOD                         1000000007
//#define int                       int64_t
#define baba_shiv                   ios_base::sync_with_stdio(false);cin.tie(NULL);
#define mpii                        map<int,int>
#define pb                          push_back
#define mkp                         make_pair
#define all(x)                      x.begin(),x.end()
#define allr(x)                     x.rbegin(),x.rend()
#define ub(v,x)                     upper_bound(all(v),x)
#define lb(v,x)                     lower_bound(all(v),x)
#define bs(v,x)                     binary_search(all(v),x)
#define gcd(a,b)                    __gcd(a,b)
#define lcm(a,b)                    (((a*b))/__gcd(a,b))
#define vi                          vector<int>
#define pii                         pair<int,int>
#define vpii                        vector<pii>
#define vs                          vector<string>
#define ff                          first
#define ss                          second
#define foru(v,s,e)                 for(int v=s;v<e;v++)
#define ford(v,s,e)                 for(int v=s;v>e;v--)
#define pi                          3.14159265358979323846
/***********************************************************************************************************************/
template < typename F, typename S >
ostream& operator << ( ostream& os, const pair< F, S > & p ) {
    return os << "(" << p.first << ", " << p.second << ")";
}

template < typename T >
ostream &operator << ( ostream & os, const vector< T > &v ) {
    os << "{";
    typename vector< T > :: const_iterator it;
    for ( it = v.begin(); it != v.end(); it++ ) {
        if ( it != v.begin() ) os << ", ";
        os << *it;
    }
    return os << "}";
}

template < typename T >
ostream &operator << ( ostream & os, const set< T > &v ) {
    os << "[";
    typename set< T > :: const_iterator it;
    for ( it = v.begin(); it != v.end(); it++ ) {
        if ( it != v.begin() ) os << ", ";
        os << *it;
    }
    return os << "]";
}

template < typename F, typename S >
ostream &operator << ( ostream & os, const map< F, S > &v ) {
    os << "[";
    typename map< F , S >::const_iterator it;
    for ( it = v.begin(); it != v.end(); it++ ) {
        if ( it != v.begin() ) os << ", ";
        os << it -> first << " = " << it -> second ;
    }
    return os << "]";
}

#define deb(x) cerr<< #x << " = " << x << endl;


/***********************************************************************************************************************/

struct CustomCompare
{
    bool operator()(pair<int, pii> &a, pair<int, pii> &b)
    {
        if (a.ff == b.ff)
            return a.ss.ff > b.ss.ss;
        return a.ff < b.ff;
    }

};
double acde(double b, double c, double theta)
{

    return sqrt(b * b + c * c - (double)2 * b * c * cos(theta * pi / (double) 180));
}
double calcAngle(double h, double m)
{
    // validate the input
    if (h < 0 || m < 0 || h > 12 || m > 60)
        printf("Wrong input");

    if (h == 12) h = 0;
    if (m == 60) m = 0;

    // Calculate the angles moved
    // by hour and minute hands
    // with reference to 12:00
    double hour_angle = 0.5 * (h * 60 + m);
    double minute_angle = 6 * m;

    // Find the difference between two angles
    double angle = abs(hour_angle - minute_angle);

    // Return the smaller angle of two possible angles
    angle = min(360 - angle, angle);

    return angle;
}



signed main()
{
    baba_shiv;

    int t = 1;
    //cin >> t;
    while (t--)
    {
        double a, b, h, m;
        cin >> a >> b >> h >> m;
        double x = calcAngle(h, m);
        /*double x = abs(h * 30 - m * 6);
        if (x > 180)
        {
            x = 360 - x;
        }
        deb(x);*/
        cout << setprecision(20) << fixed;
        cout << acde(a, b, x);

    }
    return 0;
}

Measured memory_bytes: 3616