program ABC170C
    implicit none
    integer(8)::X,N,ans,i,j,flg,diff
    integer(8),allocatable::P(:)
    read*,X,N
    if(N/=0)then
        allocate(P(N))
        read*,P
        call heapsort(N,P)
        ans=0
        diff=10000
        do i=0,110
            flg=0
            do j=1,N
                if(P(j)==i)then
                    flg=1
                    exit
                end if
            end do
            if(flg==0)then
                if(abs(i-X)<diff)then
                    diff=abs(i-X)
                    ans=i
                end if
            end if
        end do
    else
        ans=X
    end if

    print'(i0)',ans
end program ABC170C
subroutine heapsort(n,array)
    implicit none
    integer(8),intent(in) :: n
    integer(8),intent(inout) :: array(1:n)
   
    integer(8) ::i,k,j,l
    integer(8) :: t
   
    if(n.eq.1)return
  
    l=n/2+1
    k=n
    do while(k.ne.1)
       if(l.gt.1)then
          l=l-1
          t=array(L)
       else
          t=array(k)
          array(k)=array(1)
          k=k-1
          if(k.eq.1) then
             array(1)=t
             exit
          endif
       endif
       i=l
       j=l+l
       do while(j.le.k)
          if(j.lt.k)then
             if(array(j).lt.array(j+1))j=j+1
          endif
          if (t.lt.array(j))then
             array(i)=array(j)
             i=j
             j=j+j
          else
             j=k+1
          endif
       enddo
       array(i)=t
    enddo
  
    return
end subroutine heapsort