diff --git a/awk_sed.md b/awk_sed.md
index c4db186..d1be8bc 100644
--- a/awk_sed.md
+++ b/awk_sed.md
@@ -1,9 +1,15 @@
-### AWK and SED Tips and tricks
+# AWK and SED Tips and tricks
 
 ## AWK
 
-# Calculate total or average
+### Calculate total or average
 
 ```sh
 awk '{sum+=$1; n++} END {print sum / n}'
-```
\ No newline at end of file
+```
+
+or using builtin row counter NR
+
+```sh
+awk '{sum+=$1} END {{if NR > 0} print sum / NR}'
+```