diff --git a/input/4.txt b/input/4.txt
new file mode 100644
index 0000000..29e566a
--- /dev/null
+++ b/input/4.txt
@@ -0,0 +1,1000 @@
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diff --git a/src/s4a.d b/src/s4a.d
new file mode 100644
index 0000000..f58e36a
--- /dev/null
+++ b/src/s4a.d
@@ -0,0 +1,12 @@
+module s4a;
+import util;
+
+void main() {
+    readText("input/4.txt").strip.splitter("\n")
+        .count!((line) {
+            int a, b, c, d;
+            formattedRead(line.strip, "%d-%d,%d-%d", a, b, c, d);
+            return (a >= c && b <= d) || (c >= a && d <= b);
+        })
+        .writeln;
+}
diff --git a/src/s4b.d b/src/s4b.d
new file mode 100644
index 0000000..b4258e8
--- /dev/null
+++ b/src/s4b.d
@@ -0,0 +1,12 @@
+module s4b;
+import util;
+
+void main() {
+    readText("input/4sample.txt").strip.splitter("\n")
+        .count!((line) {
+            int a, b, c, d;
+            formattedRead(line.strip, "%d-%d,%d-%d", a, b, c, d);
+            return (a <= d && c <= b);
+        })
+        .writeln;
+}