local function no()
    print("no")
    os.exit()
end

local s = ""..io.read("*l")
if s ~= s:reverse() then
    no()
end
local front_s = s:sub(1, (s:len() - 1) / 2)
if front_s ~= front_s:reverse() then
    no()
end
local back_s = s:sub((s:len() + 3) / 2, s:len())
if back_s ~= back_s:reverse() then
    no()
end

print("yes")