#include <bits/stdc++.h>

using namespace std;
using ll = unsigned long long;

int main()
{
    long double s1 = 0, s2 = 0;
    long double x1, y1, x2, y2, x3, y3, x4, y4;
    cout << setprecision(7);
    cout << fixed;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
    if (x1 == x2)
    {
        s1 = max(y1, y2) - min(y1, y2);
    }
    else if (y1 == y2)
    {
        s1 = max(x1, x2) - min(x1, x2);
    }
    else
    {
        long double h1 = max(y1, y2) - min(y1, y2), h2 = max(x1, x2) - min(x1, x2);
        h1 = h1 * h1;
        h2 = h2 * h2;
        s1 = sqrt(h1 + h2);
    }
    if (x3 == x4)
    {
        s2 = max(y3, y4) - min(y3, y4);
    }
    else if (y3 == y4)
    {
        s2 = max(x3, x4) - min(x3, x4);
    }
    else
    {
        long double h3 = max(y3, y4) - min(y3, y4), h4 = max(x3, x4) - min(x3, x4);
        h3 = h3 * h3;
        h4 = h4 * h4;
        s2 = sqrt(h3 + h4);
    }
    cout << max(s1, s2) << endl;
    return 0;
}