diff --git a/quad10/fenomens/lab/p4/energ.f90 b/quad10/fenomens/lab/p4/energ.f90
index 431a296..a57601e 100644
--- a/quad10/fenomens/lab/p4/energ.f90
+++ b/quad10/fenomens/lab/p4/energ.f90
@@ -1,5 +1,7 @@
+! Retorna, donada una matriu d'spins S d'un sistema de mida LxL,
+! l'energia del sistema.
 real*8 function energ(S, L)
-  integer*2 :: S(1:64, 1:64)
+  integer*2 :: S(1:128, 1:128)
   integer*4 :: I, J, L, PBC
   real*8 :: ENE
   ENE = 0.0d0