function mydeleteat!(A,a)
    for i in a:length(A)-1
        A[i] = A[i+1]
    end
    A[length(A)] = Nothing
end

function myinsert!(A,a,c)
    b = A[end]
    for i in length(A)-1:a
        A[i+1] = A[i]
    end
    A[a] = c
    A=vcat(A,b)
    return A
end