Median filter on Image

clear all;
close all;
clc;
a=imread('rice.png');
b=im2double(a);
b=imnoise(b,'salt & pepper',0.3);
[m n]=size(b);
for i=1:m
for j=1:n
s=0;con=0;
for k= i-1:i+1
for p=j-1:j+1
if (k>0 && p>0) &&(k<m &&p<n)
con=con+1;
s(con)=b(k,p);
end
end
end
c(i,j)=median(s);
end
end
figure,imshow(b);
figure,imshow(c);