diff --git a/.gitignore b/.gitignore
index 9b79cfb..5ce5fd7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 .vscode/
-*.exe
\ No newline at end of file
+*.exe
+*.inp
+*.oac
+*.out
diff --git a/Chapter 1 Arrays and strings/hackerrank/counter.py b/Chapter 1 Arrays and strings/hackerrank/counter.py
new file mode 100644
index 0000000..5e84b22
--- /dev/null
+++ b/Chapter 1 Arrays and strings/hackerrank/counter.py	
@@ -0,0 +1,23 @@
+# Python > Collections > collections.Counter()
+# Use a counter to sum the amount of money earned by the shoe shop owner.
+#
+# https://www.hackerrank.com/challenges/collections-counter/problem
+
+from collections import Counter
+
+def calc_shoes():
+    input() # no. of shoes not used
+    shoes = Counter(input().split())
+
+    money = 0
+    for _ in range(int(input())):
+        shoe, price = input().split()
+        if shoe in shoes:
+            shoes[shoe] -= 1
+            if shoes[shoe] >= 0:
+                money += int(price)
+
+    return money
+
+if __name__ == "__main__":
+    print(calc_shoes())