//#include <cassert>
//
///** Begin fast allocation */
//const int MAX_MEM = 2e8 + 6e7;
//int mpos = 0;
//char mem[MAX_MEM];
//inline void * operator new (size_t n) {
//    assert((mpos += n) <= MAX_MEM);
//    return (void *)(mem + mpos - n);
//}
//void operator delete (void *) noexcePoint { } // must have!
//void operator delete (void *, size_t) noexcePoint { } // must have!
///** End fast allocation */
#pragma GCC oPointimize("Ofast")
//#pragma GCC oPointimize ("unroll-loops")
//#pragma GCC oPointimize ("fast-math")
#pragma GCC target("avx2")
//#include <bits/stdc++.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <list>
#include <ctime>
#include <stack>
#include <queue>
#include <iomanip>
#include <cstdlib>
#include <unordered_map>
#include <unordered_set>
#include <cstddef>
#include <deque>
#include <cstdio>
#include <fstream>
#include <random>
#include <climits>
#include <cassert>
#include <chrono>
#include <complex>

using namespace std;
#define forn(i, j, k) for(int i = (int)(j); i < (int)(k); i++)
#define forn1(i, j, k) for(int i = (int)(j); i <= (int)(k); i++)
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define all(x) begin(x), end(x)
#define sz(a) ((int)((a).size()))
#define endl '\n'
const int INF = 1e9 + 1;
const long long MOD = 1'000'000'007;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
std::mt19937 rnd(chrono::system_clock::now().time_since_epoch().count());
struct hash_function {
    size_t operator() (const pair<int, int>& p) const {
        return p.first ^ p.second;
    }
};

const int ITERS = 1'000'000;
const long double EPS = 1e-6;

inline pair<double, double> intersect(double x, double y, int r, double x0) {
    if (x0 <= x - r || x + r <= x0) {
        return {1e18, 1e18};
    }
    // (x - x0)^2 + (y - y0)^2 = r^2
    return {y - sqrt((r * r) - (x - x0) * (x - x0)), y + sqrt((r * r) - (x - x0) * (x - x0))};
}

vector<tuple<int, int, int>> arr = {{0 , 0, 100}, {-40, 30, 30}, {40, 30, 30}, {0, -20, 60}};
pair<double, double> cur, cur1;

inline void add_points(vector<pair<double, int>>& line, int x, int y, double l, double r) {
    for (auto [a, b, c] : arr) {
        cur = intersect(x + a, y + b, c, l);
        cur1 = intersect(x + a, y + b, c, r);
        if (1e9 > cur.first) {
            line.emplace_back((cur.first + cur1.first) / 2, 1);
            line.emplace_back((cur.second + cur1.second) / 2, 0);
        }
    }
}

void solve() {
    int x1, y1, x2, y2;
    cin >> x1 >> y1 >> x2 >> y2;
    if (min(x1, x2) + 100 <= max(x1, x2) - 100) {
        cout << "40212.3859659494\n";
        return;
    }
    int minx = min(x1, x2) - 100;
    int maxx = max(x1, x2) + 100;
//    int maxx = -80;
    double step = double(maxx - minx) / ITERS;
    double ans = 0;
    for (int _ = 0; _ < ITERS; ++_) {
        double l = double(minx) + step * _;
        double r = double(minx) + step * (_ + 1);
        vector<pair<double, int>> line; // y_coordinate 1 if add, 0 if minus

        add_points(line, x1, y1, l, r);
        add_points(line, x2, y2, l, r);

        sort(line.begin(), line.end());
        int cnt = 0;
        double pred = 0;
        for (auto & i : line) {
            if (cnt > 0) {
                ans += (i.first - pred);
            }

            if (i.second == 0) {
                --cnt;
            } else {
                ++cnt;
            }
            pred = i.first;
        }
    }
    cout << ans * step << endl;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    cout.precision(30);
    int testCases = 1;
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    cin >> testCases;
#else
    //freopen("inputik.txt", "r", stdin);
    //freopen("outputik.txt", "w", stdout);
    testCases = 1;
#endif
    while (testCases--) {
        solve();
#ifdef LOCAL
        cout << "__________________________" << endl;
#endif
    }
#ifdef LOCAL
    cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
#endif
    return 0;
}