N=gets.to_i
$x,$y=N.times.map{gets.split.map(&:to_i)}.transpose
def dist(x,y)
    res=0.0
    N.times do |i|
        d=((x-$x[i])**2+(y-$y[i])**2)**(1/2.0)
        res=res<d ? d : res
    end
    return res
end

ylrec=0.0
lx=0.0
rx=1000.0
80.times do |i|
    cl=(lx*2+rx)/3
    cr=(lx+rx*2)/3
    ly1=0.0
    ry1=1000.0
    80.times do |j|
        ccl=(ly1*2+ry1)/3
        ccr=(ly1+ry1*2)/3
        if dist(cl,ccl)>dist(cl,ccr)
            ly1=ccl
        else
            ry1=ccr
        end
    end
    ylrec=ly1
    ly1=0.0
    ry1=1000.0
    80.times do |j|
        ccl=(ly1*2+ry1)/3
        ccr=(ly1+ry1*2)/3
        if dist(cr,ccl)>dist(cr,ccr)
            ly1=ccl
        else
            ry1=ccr
        end
    end
    yrrec=ly1
    if dist(cl,ylrec)<dist(cr,yrrec)
        rx=cr
    else
        lx=cl
    end
end
puts dist(lx,ylrec)
