integer::N,M,i,pos
  integer,allocatable::A(:)
  read *, N, M
  allocate(A(M))
  read *, A
  pos = 1
  do i=M,1,-1
     if (pos.eq.1) then
        pos = A(i)
     else if(pos.le.A(i)) then
        pos = pos-1
     end if
  end do
  print '(i0)',pos
end program