diff --git a/2017/01.cpp b/2017/01.cpp
new file mode 100644
index 0000000..459b6ae
--- /dev/null
+++ b/2017/01.cpp
@@ -0,0 +1,54 @@
+#include <cstddef>
+#include <cstdint>
+#include <iostream>
+#include <string>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+auto Captcha(std::string const& input, std::size_t offset) -> std::int64_t {
+  std::int64_t acc = 0;
+  std::size_t const n = input.size();
+  for (std::size_t i = 0; i < n; ++i) {
+    if (input[i] == input[(i+offset)%n]) {
+      acc += input[i] - '0';
+    }
+  }
+  return acc;
+}
+
+auto Part1(std::string const& input) -> std::int64_t {
+  return Captcha(input, 1);
+}
+
+auto Part2(std::string const& input) -> std::int64_t {
+  return Captcha(input, input.size() / 2);
+}
+
+} // namespace
+
+TEST_SUITE("2017-01 examples") {
+  TEST_CASE("part 1") {
+    CHECK(Part1("1122") == 3);
+    CHECK(Part1("1111") == 4);
+    CHECK(Part1("1234") == 0);
+    CHECK(Part1("91212129") == 9);
+  }
+  TEST_CASE("part 2") {
+    CHECK(Part2("1212") == 6);
+    CHECK(Part2("1221") == 0);
+    CHECK(Part2("123425") == 4);
+    CHECK(Part2("123123") == 12);
+    CHECK(Part2("12131415") == 4);
+  }
+}
+
+auto main(int argc, char** argv) -> int {
+  std::string input;
+  std::getline(*aocpp::Startup(argc, argv), input);
+  std::cout << "Part 1: " << Part1(input) << std::endl;
+  std::cout << "Part 2: " << Part2(input) << std::endl;
+}