#include <iostream>
#include <vector>
#include <map>
#include <unordered_map>
#include <queue>
#include <set>
#include <algorithm>
#include <string>
#include <math.h>
#include <limits.h>
#include <stack>
#include <complex>
#include <stdlib.h>
#include <stdio.h>
#include <functional>
#include <cfloat>
#include <math.h>
#include <numeric>
#include <string.h>
#include <sys/time.h>
#include <random>


#define fs first
#define sc second
// #define endl "\n"

using namespace std;

typedef long long ll;
typedef unsigned int uint;
typedef pair<ll, ll> P;


class modInt{
    ll value;
    static const ll mod = 1000000007;

public:
    modInt(ll x=0): value{x % mod}{}

    inline modInt& operator+=(modInt x){
        value = (value + x.value) % mod;
        return *this;
    }

    inline modInt& operator-=(modInt x){
        value = (value + mod - x.value) % mod;
        return *this;
    }

    inline modInt& operator*=(modInt x){
        value = (value * x.value) % mod;
        return *this;
    }


    inline modInt operator/=(modInt x){
        *this *= x.inv();
        return *this;
    }

    inline modInt pow(modInt x, int n){
        modInt res = modInt(1LL);
        while(n > 0){
            if(n & 1)   res *= x;
            x *= x;
            n >>= 1;
        }
        return res;
    }

    inline modInt inv(){
        modInt res = pow(value, mod-2);
        return res;
    }

    inline ll get(){
        return value;
    }
};

modInt operator+(modInt x, modInt y){
    return x += y;
}

modInt operator-(modInt x, modInt y){
    return x -= y;
}

modInt operator*(modInt x, modInt y){
    return x *= y;
}

modInt operator/(modInt x, modInt y){
    return x /= y;
}

ostream& operator<<(ostream& os, modInt x){
    return os << x.get();
}


class modIntCombinations{
    vector<modInt> factArray;

    void make_fact(ll x){
        for(auto i = factArray.size(); i <= x+1; i++){
            modInt y = factArray[i-1] * i;
            factArray.push_back(y);
        }
    }

public:
    modIntCombinations(){
        factArray.emplace_back(1);
    }

    modInt fact(ll x){
        if(factArray.size() < x+1){
            make_fact(x);
        }
        return factArray[x];
    }

    modInt comb(ll n, ll k){
        if(n < k){
            return modInt{0};
        }
        else{
            return fact(n) / fact(k) / fact(n - k);
        }
    }

    modInt perm(ll n, ll k){
        if(n < k){
            return modInt{0};
        }
        else{
            return fact(n) / fact(k);
        }
    }
};

// a と b の最大公約数を返す
ll gcd(ll a, ll b) {
    if (b == 0) return a;
    else return gcd(b, a % b);
}


ll lcm(ll a, ll b){
    return a / gcd(a, b) * b;
}



// 素数判定
bool is_prime(ll N) {
    if (N == 1) return false;
    for (ll i = 2; i * i <= N; ++i) {
        if (N % i == 0) return false;
    }
    return true;
}


// 約数列挙
vector<ll> enum_divisors(ll N) {
    vector<ll> res;
    for (ll i = 1; i * i <= N; ++i) {
        if (N % i == 0) {
            res.push_back(i);
            if (N/i != i) res.push_back(N/i);
        }
    }
    sort(res.begin(), res.end());
    return res;
}


// 素因数分解
vector<pair<ll, ll>> prime_factorize(ll N){
    vector<pair<ll, ll>> res;
    for(ll i = 2; i * i <= N; i++){
        if(N % i != 0)  continue;
        ll ex = 0;

        while(N % i == 0){
            ex++;
            N /= i;
        }

        res.push_back({i, ex});
    }

    if(N != 1)  res.push_back({N, 1});
    return res;
};

const double pi=3.14159265358979323846;

int main(){
    double a, b, h, m;
    cin >> a >> b >> h >> m;

    double p = (2.0 * pi) * ((h * 60.0) + m) / (12.0 * 60.0);
    double q = (2.0 * pi) * m / 60.0;

    double ax = a * cos(p), ay = a * sin(p);
    double bx = b * cos(q), by = b * sin(q);

    double res = sqrt((ax - bx) * (ax - bx) + (ay - by) * (ay - by));

    printf("%.15f\n", res);


    return 0;
}


Measured memory_bytes: 4140