// JavaProgram.cpp
// Author : Priydarshi Singh (@dryairship)
// One cat just leads to another. One bug leads to two others.

#include <bits/stdc++.h>
using namespace std;

// I like my types defined.
typedef long long           ll;
typedef pair<int, int>      pii;
typedef pair<ll, ll>        pll;
typedef vector<int>         vi;
typedef vector<ll>          vl;
typedef vector<pii>         vii;
typedef vector<pll>         vll;
typedef set<int>            si;
typedef map<string, int>    msi;
typedef map<int, int>       mii;

// Traditional science is all about finding "hashtag define"s.
#define fr(i, n)            for(int i=0; i<(n); ++i)
#define frC(i, n, c)        for(int i=0; (i<(n)) && (c); ++i)
#define frA(i, a, n)        for(int i=a; i<=(n); ++i)
#define frD(i, a, n)        for(int i=a; i>=(n); --i)
#define fill(a)             memset(a, 0, sizeof(a))
#define fill1(a)            memset(a, -1, sizeof(a))
#define revsort(a, b)       sort(a, b, greater<int>())
#define ff                  first
#define ss                  second
#define pb                  push_back 
#define dout                if(DEBUGGING) cout
#define dbg                 if(DEBUGGING) 
#define endl                "\n"

// When you realize MOD > INF...
int DEBUGGING    =          0;
const int INF    =          1000000000;
const int MOD    =          1000000007;
const ll LINF    =          1e18;
const double PI  =          3.1415926535897932;
const double EPS =          1e-7;

// I'D SPAM. Hehe.
ll gcdEx                    (ll a, ll b, ll *x, ll *y){if(!a){*x=0;*y=1;return b;} 
ll x1,y1,gcd=gcdEx          (b%a,a,&x1,&y1); *x=y1-(b/a)*x1;*y=x1; return gcd;}
ll modI(ll b, ll m)         {ll x,y;gcdEx(b,m,&x,&y);return (x%m+m)%m;}
ll modD(ll a, ll b)         {return (modI(b,MOD)*(a%MOD))%MOD;}
ll modS(ll a, ll b)         {return ((a%MOD)-(b%MOD)+MOD)%MOD;}
ll modP(ll x, ll y)         {ll r=1; x%=MOD; while(y>0){if(y&1){r=(r*x)%MOD;} y=y>>1; x=(x*x)%MOD;} return r;}
ll modA(ll a, ll b)         {return ((a%MOD)+(b%MOD))%MOD;}
ll modM(ll a, ll b)         {return ((a%MOD)*(b%MOD))%MOD;}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

//https://www.geeksforgeeks.org/calculate-angle-hour-hand-minute-hand/
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;  
}  

void solve(int TEST_CASE){
    int a,b,h,m;
    cin >> a >> b >> h >> m;
    double ang = calcAngle(h,m);
    double dist = sqrt(a*a + b*b - 2*a*b*cos(ang*PI/180));
    cout <<setprecision(20)<< dist;
}

int main(int argc, char* argv[]){
    if(argc==2 && argv[1][1]=='v') DEBUGGING = 1;
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    cin.exceptions(cin.failbit);
    int nTestCases=1;
    //cin >> nTestCases;
    frA(i,1,nTestCases) solve(i);
    return 0;
}

Measured memory_bytes: 4192