diff --git a/The Last Algorithms Course You'll Need/5. Two Crystal Balls.c b/The Last Algorithms Course You'll Need/5. Two Crystal Balls.c
index d3501c2..af60ea9 100644
--- a/The Last Algorithms Course You'll Need/5. Two Crystal Balls.c	
+++ b/The Last Algorithms Course You'll Need/5. Two Crystal Balls.c	
@@ -1,6 +1,19 @@
 #include <math.h>
 #include <stdio.h>
 
+// complexity is O(sqrt(N))
+// well we need ot find an exact moment,
+// let's say "height" at which our crystal
+// balls break, for that we only have 2 balls,
+// so we can't do binary search, since the range
+// is tooooo huge, therefore we run a linear
+// growth bigger than N, but small enough to find where
+// the first ball breaks, then we take the interval
+// between: [the previous non-break] and [where it broken]
+// and run a normal linear search
+// therefore we run sqrt(n) + sqrt(n) times
+// so it's O(sqrt(N)
+
 #define SIZE 999
 
 int two_crystal_balls_search(int array[], int size, int value)