function [g,b] = sqgrid(n)
g=zeros(n);
b=4*n-4;
for i=1:n-1
        g(i,1) = i;
        g(n,i) = i + n - 1;
        g(n-i+1,n) = i + 2*n - 2;
        g(1,n-i+1) = i + 3*n - 3;
end;
k=b+1;
for j=2:n-1
    for i=2:n-1
        g(i,j) = k;
        k = k + 1;
    end;
end;