diff --git a/04/d.py b/04/d.py
new file mode 100644
index 0000000..e9943ba
--- /dev/null
+++ b/04/d.py
@@ -0,0 +1,28 @@
+import os
+
+pairs = open(os.path.dirname(__file__) +
+             "/input.txt", "r").read().splitlines()
+
+tot1 = 0
+tot2 = 0
+
+for p in pairs:
+    a = p.split(",")
+
+    arrays = []
+
+    for i in range(0, len(a), 1):
+        b = a[i].split("-")
+
+        if b[0] == b[1]:
+            arrays.append([int(b[0])])
+            continue
+        arrays.append(range(int(b[0]), int(b[1])+1))
+
+    set_a = set(arrays[0])
+    set_b = set(arrays[1])
+
+    if (set_a.issubset(set_b) or set_b.issubset(set_a)):
+        tot1 += 1
+
+print("First answer: " + tot1)