local n = io.read("*n")
local str = {}
for i = 1, n do
    table.insert(str, io.read("l"))
end
local firStr = str[1]
local len = string.len(firStr)
local endStr = string.sub(firStr, len, len)
local tab = {}
tab[firStr] = 1
local result = true
for i = 2,n do
    local tStr = str[i]
    local t = string.sub(tStr, 1, 1)
    if t == endStr or tab[tStr] then
        print("No")
        result = false
        break
    end
    len = string.len(tStr)
    endStr = string.sub(tStr, len, len)
end
if result then
    print("Yes")
end