program ABC109B
    implicit none
    integer(8)::N,i,j
    integer(8)::flg=0
    character(10),allocatable,dimension(:)::W

    read(5,*)N
    allocate(W(N))

    do i=1,N
        read(5,*)W(i)
        if(i>1 .and. flg==0)then
            if(W(i-1)(len_trim(W(i-1)):len_trim(W(i-1)))/=W(i)(1:1))then
                flg=1
            else
                do j=1,i-1
                    if(W(i)==W(j))then
                        flg=1
                        exit
                    end if
                end do
            end if
        end if
    end do

    if(flg==0)then
        print'(A)',"Yes"
    else
        print'(A)',"No"
    end if
end program ABC109B