How do I vertically segment a image in three parts?

% paper split
img = imread('paper.jpg');
%imshow(img, []);
[nrows ncols dim] = size(img);
% Get the slices colums wise split equally
img1 = img(:,1:ncols/3,:);
img2 = img(:,(ncols/3)+1:2*ncols/3,:);
img3 = img(:,(2*ncols/3)+1:ncols,:);
figure,
subplot(1,3,1), imshow(img1,[]); title('first part');
subplot(1,3,2), imshow(img2,[]); title('second part');
subplot(1,3,3), imshow(img3,[]); title('third part');