#include <bits/stdc++.h>

// definitions
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define rep(i, l, r) for (long long i = (l); i < (long long)(r); i++)
#define repb(i, r, l) for (long long i = (r); i > (long long)(l); i--)
#define pb push_back
#define pf push_front
#define mod1 998244353
#define mod 1000000007
#define MAX_CHAR 256


using namespace std;
typedef vector<long long> vl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector< pair<long long, long long> > vp;
typedef vector<tuple<long long , long long , long long> > vtup;
typedef deque <long long> dql;
typedef deque <char> dqc;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;


// prevent collisions in unordered_map
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

typedef unordered_map <long long, long long, custom_hash> umap;


// standard functions
ll mystoi(string str)
{
    stringstream ss(str);
    ll ans=0;
    ss >> ans;

    return ans;
}


ll exp(ll x, ll ex) {
    ll ans = 1ll;
    while (ex > 0) {
        if (ex & 1ll) ans = (ans * x);
        ex >>= 1ll;
        x = (x * x);
    }
    return ans;
} 
 
ll nCrModp(ll n, ll r, ll p) 
{ 
    ll C[r+1]; 
    memset(C, 0, sizeof(C)); 
  
    C[0] = 1; 
    for (ll i = 1; i <= n; i++) 
    { 
        for (ll j = min(i, r); j > 0; j--) 
            C[j] = (C[j] + C[j-1])%p; 
    } 
    return C[r]; 
}
 
bool isPrime(ll n) 
{ 
    if (n <= 1)  return false; 
    if (n <= 3)  return true;  
    if (n%2 == 0 || n%3 == 0) return false; 
  
    for (ll i=5; i*i<=n; i=i+6) 
        if (n%i == 0 || n%(i+2) == 0) 
           return false; 
  
    return true; 
}

bool sort_cond(const pair<ll,ll> &a, const pair <ll,ll> &b)
{
    return a.second > b.second;
}

const ll MAXSIEVE=(1e3+5);
ll spf[MAXSIEVE];
void sieve() 
{ 
    spf[1] = 1; 
    for (ll i=2; i<MAXSIEVE; i++) 
        spf[i] = i; 

    for (ll i=4; i<MAXSIEVE; i+=2) 
        spf[i] = 2; 
  
    for (ll i=3; i*i<MAXSIEVE; i++) 
    { 
        if (spf[i] == i) 
        { 
            for (ll j=i*i; j<MAXSIEVE; j+=i) 
                if (spf[j]==j) 
                    spf[j] = i; 
        } 
    } 
}

float polydiagonal(float n, float a) 
{ 
  
    // Side and side length cannot be negative 
    if (a < 0 && n < 0) 
        return -1; 
  
    // diagonal 
    // degree converted to radians 
    return 2 * a * sin((((n - 2) * 180) / (2 * n)) * 3.14159 / 180); 
} 


// code beigns in main
int main()
{

    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    ll t=1;
    // cin >> t;
    ld pi=3.14159265358979323846264;
    while(t--)
    {
        ld a,b,h,m;
        cin >> a >>b >>h >> m;

        ld ha=(h*(2*pi))/12.0+((2*pi*m)/(12*60));
        ld ma=(m*(2*pi))/60.0;

        // cout << ha << endl;
        // cout << ma << endl;

        ld diff=abs(ha-ma);
        // cout << diff << endl;

        ld c=a*a;
        c+=b*b;
        c-=2*a*b*cos(diff);
        c=sqrt(c);

        cout << setprecision(15) <<c << endl;
    }
}


Measured memory_bytes: 4160