diff --git a/2017/13.cpp b/2017/13.cpp
new file mode 100644
index 0000000..682d578
--- /dev/null
+++ b/2017/13.cpp
@@ -0,0 +1,79 @@
+#include <cstdint>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <tuple>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+
+using namespace aocpp;
+
+namespace {
+
+struct Scanner {
+  std::uint64_t depth, range, position, length;
+};
+
+auto Parse(std::istream & in)
+-> std::vector<Scanner>
+{
+  std::uint64_t depth, range;
+  char skip;
+  std::vector<Scanner> result;
+  while (in >> depth >> skip >> range) {
+    auto len = range*2-2;
+    result.push_back(Scanner{depth, range, depth%len, len});
+  }
+  return result;
+}
+
+auto Caught(std::vector<Scanner> const& scanners) -> std::size_t {
+  std::uint64_t severity = 0;
+  for (auto const& scanner : scanners) {
+    if (scanner.position == 0) {
+      severity += scanner.depth * scanner.range;
+    }
+  }
+  return severity;
+}
+
+auto Delay(std::vector<Scanner> & scanners) {
+  std::uint64_t delay = 0;
+
+  for (;;) {
+    bool success = true;
+    for (auto & scanner : scanners) {
+      if (scanner.position++ == 0) { success = false; }
+      if (scanner.position == scanner.length) scanner.position = 0;
+    }
+    if (success) break;
+    delay++;
+  }
+
+  return delay;
+}
+
+} // namespace
+
+TEST_SUITE("2017-12 examples") {
+  TEST_CASE("example") {
+    std::istringstream in {
+      "0: 3\n"
+      "1: 2\n"
+      "4: 4\n"
+      "6: 4\n"      
+    };
+    auto input = Parse(in);
+    CHECK(Caught(input) == 24);
+    CHECK(Delay(input) == 10);
+  }
+}
+
+auto main(int argc, char** argv) -> int {
+  auto input = Parse(*Startup(argc, argv));
+  std::cout << "Part 1: " << Caught(input) << std::endl;
+  std::cout << "Part 2: " << Delay(input) << std::endl;
+}
\ No newline at end of file
diff --git a/2017/CMakeLists.txt b/2017/CMakeLists.txt
index cbd2fb4..9271f54 100644
--- a/2017/CMakeLists.txt
+++ b/2017/CMakeLists.txt
@@ -13,6 +13,9 @@ target_link_libraries(2017_11 aocpp)
 add_executable(2017_12 12.cpp)
 target_link_libraries(2017_12 aocpp)
 
+add_executable(2017_13 13.cpp)
+target_link_libraries(2017_13 aocpp)
+
 add_executable(2017_14 14.cpp)
 target_link_libraries(2017_14 aocpp knothash)