diff --git a/2017/day13.py b/2017/day13.py
new file mode 100644
index 0000000..de669c9
--- /dev/null
+++ b/2017/day13.py
@@ -0,0 +1,29 @@
+with open("input/day13.txt") as f:
+    input = f.read()
+
+scanners = {}
+
+for line in input.splitlines():
+    parts = line.split(": ")
+    d, r = int(parts[0]), int(parts[1])
+
+    assert d not in scanners, "no overlapping scanners"
+    scanners[d] = r
+
+
+def part1(scanners):
+    severity = 0
+    for d in range(max(scanners.keys()) + 1):
+        r = scanners.get(d)
+        if r is None:
+            continue
+
+        assert r > 1, r
+        cycle = (r - 1) * 2
+        pos = d % cycle
+        if pos == 0:
+            severity += d * r
+    return severity
+
+
+print(part1(scanners))