diff --git a/OUTPUT b/OUTPUT
index a2494d2..f610ba2 100644
--- a/OUTPUT
+++ b/OUTPUT
@@ -443,3 +443,11 @@ ex1.bash : res=285
 ex2.bash : res=412
 	time: 0:03.37 real, 3.34 user, 0.03 sys
 	context-switch:	19+1, page-faults: 0+11909
+
+=========================================
+================= day20 =================
+=========================================
+
+ex1.bash : res=5966506063747
+	time: 0:00.54 real, 0.53 user, 0.00 sys
+	context-switch:	1+1, page-faults: 0+223
diff --git a/day20/Makefile b/day20/Makefile
index 224acfb..62c581b 100644
--- a/day20/Makefile
+++ b/day20/Makefile
@@ -20,7 +20,7 @@ ex1:
 	@#$(TIME) ex1-c 2020 < $(INPUT) 2>&1
 
 ex2:
-	@$(TIME) ex2.bash < $(INPUT) 2>&1
+	@#$(TIME) ex2.bash < $(INPUT) 2>&1
 	@#$(TIME) ex1-c 30000000 < $(INPUT) 2>&1
 
 clean:
diff --git a/day20/OUTPUT b/day20/OUTPUT
new file mode 100644
index 0000000..3c22426
--- /dev/null
+++ b/day20/OUTPUT
@@ -0,0 +1,4 @@
+ex1.bash : res=5966506063747
+	time: 0:00.54 real, 0.53 user, 0.00 sys
+	context-switch:	1+1, page-faults: 0+223
+
diff --git a/day20/ex1.bash b/day20/ex1.bash
index 589dfff..ecf642d 100755
--- a/day20/ex1.bash
+++ b/day20/ex1.bash
@@ -54,18 +54,21 @@ for key in "${!nums[@]}"; do
 
 done
 
-ALL=("${T[@]}" "${R[@]}" "${B[@]}" "${L[@]}" "${RT[@]}" "${RR[@]}" "${RB[@]}" "${RL[@]}")
+ALL="${T[@]} ${R[@]} ${B[@]} ${L[@]} ${RT[@]} ${RR[@]} ${RB[@]} ${RL[@]}"
+ALLSIZE=${#ALL}
+
 declare -i res=1 count
 for ((i=0; i<${#nums[@]}; ++i)); do
     count=0
 
     for t in ${T[$i]} ${R[$i]} ${B[$i]} ${L[$i]}; do
-        for s in "${ALL[@]}"; do
-            [[ $t == "$s" ]] && ((count++))
-        done
+        # https://stackoverflow.com/questions/26212889/bash-counting-substrings-in-a-string/50601141#50601141
+        S=${ALL//$t}
+        # 10 is line size
+        ((count += (ALLSIZE-${#S})/10))
     done
-
-    ((count ==6)) && ((res*=${nums[$i]}))
+    # 6 is 4 for itself, + 2 for other matching
+    ((count == 6)) && ((res*=${nums[$i]}))
 done
 
 printf "%s : res=%d\n" "$CMD" "$res"