program main
	integer :: n, i, j, d
    read(*,*) n
    if(mod(n,2) == 1) then
    	write(*,*) -1
        stop
    endif
    
    do j = 1, n
    	do i = 1, n
        	if(abs(i-j)<=1) then
        	if(i==j) then
            	if (mod(i,2) ==1) then
        			write(6,'a',advance="no") 'a'
                else
                	write(6,'a',advance="no") 'b'
                end if
            else if(i==j-1) then
        			write(6,'a',advance="no") 'a'
			else 
            	write(6,'a',advance="no") 'a'
            end if
            else
                write(6,'a',advance="no") '.'
           	end if
            end do
            end do
             end program main