function c = strass(a,b)
nmin = 16;
format long;
[n,n] = size(a);
if n <= nmin;
   c = a*b;
else
   m = n/2; u = 1:m; v = m+1:n;
   p1 = strass(a(u,u)+a(v,v),b(u,u)+b(v,v));
   p2 = strass(a(v,u)+a(v,v),b(u,u));
   p3 = strass(a(u,u),b(u,v)-b(v,v));
   p4 = strass(a(v,v),b(v,u)-b(u,u));
   p5 = strass(a(u,u)+a(u,v),b(v,v));
   p6 = strass(a(v,u)-a(u,u),b(u,u)+b(u,v));
   p7 = strass(a(u,v)-a(v,v),b(v,u)+b(v,v));
   c = [p1+p4-p5+p7,p3+p5; p2+p4, p1-p2+p3+p6];
end