diff --git a/four.py b/four.py
new file mode 100755
index 0000000..b751177
--- /dev/null
+++ b/four.py
@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+from useful import *
+
+def does_overlap(l):
+    a, b, c, d = (int(n) for n in re.match(r'(\d+)-(\d+),(\d+)-(\d+)', l).groups())
+    u = set(i for i in range(a, b + 1))
+    v = set(i for i in range(c, d + 1))
+    return u & v == u or u & v == v
+
+def sorta_overlap(l):
+    a, b, c, d = (int(n) for n in re.match(r'(\d+)-(\d+),(\d+)-(\d+)', l).groups())
+    u = set(i for i in range(a, b + 1))
+    v = set(i for i in range(c, d + 1))
+    return 1 if u & v else 0
+
+ls = lines(open(0))
+print(sum(does_overlap(l) for l in ls))
+print(sum(sorta_overlap(l) for l in ls))
diff --git a/input4 b/input4
new file mode 100644
index 0000000..a03fd58
--- /dev/null
+++ b/input4
@@ -0,0 +1,1000 @@
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