diff --git a/The Last Algorithms Course You'll Need/4. Binary Search.c b/The Last Algorithms Course You'll Need/4. Binary Search.c
index b15f400..76ebc11 100644
--- a/The Last Algorithms Course You'll Need/4. Binary Search.c	
+++ b/The Last Algorithms Course You'll Need/4. Binary Search.c	
@@ -2,6 +2,10 @@
 
 #define SIZE 4096
 
+// The complexity is O(log n)
+// because we always half the amount
+// like N/2 -> N/4 -> N/8 ... N/(2^k) which equals log n
+
 int binary_search(int array[], int size, int offset, int value)
 {
 	int pivot = size / 2;