p -1;exit
gets
d = gets.split.map(&:to_i)
x1,y1 = gets.split.map(&:to_i)
z = [x1+y1,x1-y1].map(&:abs).max

if z==0
    p 0;exit
end

d.each{|de|
    if z==de
        p 1;exit
    end
}

dmax = d.max

if (z<dmax)
    p 2;exit
end

if (((z+dmax-1)/dmax) <= 2)
    p ((z+dmax-1)/dmax)
else
    p -1
end