print((function (f, fh)
	local a,r={},10e5+1
	for i=1,fh:read("*n") do a[i]=fh:read("*n") end
	table.sort(a)
	for i=1,#a-1 do r=f(a,i,r) end
	return r~=10e5+1 and r or 0
end)(function (a, i, n)
	return (a[i+1]-a[i]<n and a[i+1]-a[i]~=0) and a[i+1]-a[i] or n
end, io.stdin))