diff --git a/aoc.cpp b/aoc.cpp
index b02fb54..1c61b01 100644
--- a/aoc.cpp
+++ b/aoc.cpp
@@ -8,12 +8,12 @@
 
 #include "fmt/format.h"
 
-using levels_t  = std::vector<std::uint32_t>;
+using levels_t  = std::vector<std::int32_t>;
 using reports_t = std::vector<levels_t>;
 
 auto main([[maybe_unused]]int argc, [[maybe_unused]]char const* argv[]) -> int {
     constexpr auto filename = "./dat/24/ex/02.txt";
-    std::ifstream strm{filename, std::ios::in};
+    std::ifstream strm{filename, std::ios::in | std::ios::binary};
     if (!strm.is_open()) {
         fmt::print("Error opening file: {}\n", filename);
         return 1;
@@ -21,7 +21,7 @@ auto main([[maybe_unused]]int argc, [[maybe_unused]]char const* argv[]) -> int {
 
     reports_t reports{};
 
-    levels_t levels{};
+    levels_t tmp{};
     std::string str{};
     while (strm) {
         auto const c = char(strm.peek());
@@ -29,20 +29,63 @@ auto main([[maybe_unused]]int argc, [[maybe_unused]]char const* argv[]) -> int {
             str += char(strm.get());
             continue;
         }
-        if (c == ' ') {
-            if (!str.empty()) {
-                levels.emplace_back(std::stoi(str));
-                str.clear();
-            }
+        if (c == ' ' && !str.empty()) {
+            tmp.emplace_back(std::stoi(str));
+            str.clear();
         }
-        if (c == '\n') {
-            if (!str.empty()) {
-                reports.emplace_back(std::move(levels));
-                str.clear();
-            }
+        if (c == '\n' && !str.empty()) {
+            tmp.emplace_back(std::stoi(str));
+            reports.emplace_back(std::move(tmp));
+            str.clear();
         }
         strm.get();
     }
 
+    // auto diff = reports | std::views::transform([](auto const& levels) {
+    //     return levels | std::views::slide(2) | std::views::transform([](auto pair) {
+    //         return pair[1] - pair[0];
+    //     });
+    // });
+
+    auto diff = reports | std::views::transform([](auto const& levels) {
+        return levels | std::views::adjacent_transform<2>([](auto const& a, auto const& b) {
+            return b - a;
+        });
+    });
+
+    // condition: all increasing or all decreasing.
+    auto incdec = diff | std::views::filter([](auto const& levels) {
+        auto const n = std::ranges::all_of(levels, [](auto v) { return v < 0; });
+        auto const p = std::ranges::all_of(levels, [](auto v) { return v > 0; });
+        return n || p;
+    });
+
+    // condition: Any two adjacent levels differ by at least one and at most three.
+    auto adjdiff = incdec | std::views::filter([](auto const& levels){
+        return std::ranges::all_of(levels, [](auto v) {
+            return std::abs(v) <= 3;
+        });
+    });
+
+    auto const safe_reports = std::ranges::distance(adjdiff);
+
+    fmt::print("Part A: {}\n", safe_reports);
+
+    for (auto levels : reports) {
+        for (auto level : levels) {
+            fmt::print("{} ", level);
+        }
+        fmt::print("\n");
+    }
+
+    fmt::print("--------------------------------------------------------------------------------\n");
+
+    for (auto levels : diff) {
+        for (auto level : levels) {
+            fmt::print("{} ", level);
+        }
+        fmt::print("\n");
+    }
+
     return 0;
 }