diff --git a/homework4.txt b/homework4.txt
index d8160f0..0ce7bc3 100644
--- a/homework4.txt
+++ b/homework4.txt
@@ -1,2 +1,6 @@
 1. What is .gitignore? You can write the answer either in Korean or English.
-2. Why do Github users need an SSH key pair? (Users can use either SSH key pair or github account info.) Please write down a brief explanation of SSH key.
\ No newline at end of file
+.gitignore file is a list of files that are not useful so you want to ignore in your working directory, such as backup file, log file, or complilation products.
+
+2. Why do Github users need an SSH key pair? (Users can use either SSH key pair or github account info.) Please write down a brief explanation of SSH key.
+SSH keys are pair of public key that get shared with services like GitHub, and a private key that is stored only on your computer. When keys are match, you can get access.
+SSH key is an alternate way to identify yourself so that you are not required to enter your username and password every time.
diff --git a/homework4/2019-16726.zip b/homework4/2019-16726.zip
new file mode 100644
index 0000000..cc9ffe7
Binary files /dev/null and b/homework4/2019-16726.zip differ
diff --git a/homework4/Source.cpp b/homework4/Source.cpp
index ab69b66..a2c7e19 100644
--- a/homework4/Source.cpp
+++ b/homework4/Source.cpp
@@ -3,7 +3,6 @@
 #include <time.h>
 using namespace std;
 
-
 int main()
 {
 	const int arrsize = 10;
@@ -17,17 +16,17 @@ int main()
 	}
 	cout << endl;
 
-	//Given the int array arr, generate another int array output.
-	//whose element indiciates how many elements in arr is smaller than arr[i].
-	//For example, if arr is given as [5,8,5,6,8,1,5,9,5,8], 
-	//output should be [1,6,1,5,6,0,1,9,1,6]. 
-
 	int* output = new int[arrsize];
 	cout << "Array output: ";
-
-	/***********************************
-	Implement the code here!
-	************************************/
+	for (int t = 0; t < arrsize; t++) {
+		int num = 0;
+		for (int j = 0; j < arrsize; j++) {
+			if (arr[t] > arr[j]) {
+				num++;
+			}
+		}
+		output[t] = num;
+	}
 
 	for (int i = 0; i < arrsize; i++) {
 		cout << output[i] << " ";