diff --git a/samples/random_unsolvable.txt b/samples/random_unsolvable.txt
new file mode 100644
index 0000000..2fdc4db
--- /dev/null
+++ b/samples/random_unsolvable.txt
@@ -0,0 +1,72 @@
+1 0 1 0 1 0 0 0 
+0 1 1 0 0 0 1 0 
+1 0 1 0 0 0 1 0 
+1 1 0 1 0 0 1 0 
+0 0 0 1 1 0 0 1 
+1 1 1 1 0 1 1 1 
+0 1 0 0 0 1 1 1 
+1 0 1 1 0 1 1 1 
+
+0 1 0 1 1 0 0 0 
+1 0 1 0 0 0 0 1 
+0 1 0 1 1 1 0 0 
+0 1 0 1 1 1 1 1 
+1 1 0 0 0 1 0 0 
+1 1 1 0 0 0 1 1 
+1 0 0 1 1 1 0 0 
+0 0 0 1 0 1 0 0 
+
+1 0 0 0 1 1 1 0 
+0 0 1 1 0 1 1 1 
+0 0 1 0 0 0 1 1 
+0 1 0 0 0 1 0 0 
+1 1 1 0 0 1 0 1 
+1 1 1 1 0 1 0 0 
+0 0 0 0 1 1 0 1 
+0 1 0 0 1 0 0 1 
+
+0 0 0 1 1 0 0 1 
+0 1 1 0 0 0 1 1 
+0 0 0 0 0 0 1 0 
+1 1 1 1 1 0 1 1 
+1 0 1 1 0 0 1 0 
+0 0 1 1 0 0 1 1 
+1 1 0 1 1 0 0 0 
+1 1 1 0 0 0 0 0 
+
+0 1 1 1 1 1 0 0 
+1 1 1 1 1 0 1 0 
+0 1 0 1 1 0 0 0 
+0 1 1 0 1 0 0 0 
+0 0 0 0 0 0 1 0 
+1 1 0 1 1 0 0 1 
+1 0 1 1 1 1 1 0 
+0 1 0 1 0 1 0 0 
+
+1 0 1 0 0 0 0 1 
+1 0 1 1 1 1 1 0 
+0 1 1 0 1 0 1 0 
+1 1 1 1 0 0 0 1 
+1 0 0 0 1 1 0 1 
+0 1 1 1 1 1 1 1 
+1 1 1 0 1 0 1 0 
+1 0 0 1 1 0 0 1 
+
+1 0 0 1 1 0 1 0 
+0 0 0 1 0 1 0 0 
+1 0 1 0 0 0 0 0 
+1 0 0 0 1 1 1 0 
+0 0 1 1 0 1 1 0 
+0 1 0 0 0 1 0 1 
+0 0 0 0 0 0 0 1 
+0 1 0 0 0 0 1 1 
+
+0 0 1 1 0 0 1 1 
+0 0 0 0 0 1 0 1 
+0 1 1 1 0 0 0 0 
+1 0 1 0 0 1 1 0 
+1 0 0 1 0 0 1 0 
+1 0 1 0 0 1 1 1 
+1 0 1 1 0 1 0 0 
+1 0 0 0 1 0 0 1 
+