my matlab shows matrix dimension must agree error

 my code is 
clc;
 close all; 
clear all;
 I = imread('bp3.jpg');
 j = rgb2gray(I);
 n=imread('bo6.jpg');
 m=rgb2gray(n);
 i = j - m ;
 figure, imshow(i)

i checked size of j and m and dimensions

Answer 1

[Azzi Abdelmalek]

Check the sizes of j and m

size(j)
size(m)