program strings_with_the_same_length
    implicit none
    integer(4):: n,i
    character(:),allocatable:: s,t,st
    
    read*, n
    allocate(character(n):: s, t)
    allocate(character(2*n):: st)
    read*, s,t
    
    do i=1,n
        st(2*i-1:2*i) = s(i:i)//t(i:i)
    end do
    print*, st
end program strings_with_the_same_length