Histogram Full View

My histogram is over limit (Means that it's more than the top part), this makes me cannot see what's the maximum on top of the histogram, so can I know how to show the full Histogram instead of the top part being gone? Thanks :)

This is the code I use

I = imcrop(rgb2gray(imread('1.jpg')),[1372 979 176 148]);
figure, imhist(I(:,:,1));