diff --git a/Makefile b/Makefile
index 057cf6b..b8b2f06 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,17 @@
+COMMON_OPT_FLAGS?= -O3 -march=native -pipe -flto \
+	 -march=native -fgraphite -fopenmp -floop-parallelize-all -ftree-parallelize-loops=4 \
+	 -floop-interchange -ftree-loop-distribution -floop-strip-mine -floop-block \
+	 -fno-stack-check -fno-strict-aliasing 
+
+C_OPT_FLAGS?=
+CXX_OPT_FLAGS?= -felide-constructors
+LD_OPT_FLAGS?=-O3 -flto
+
+COMMON_FLAGS=-Wall -pedantic $(COMMON_OPT_FLAGS)
+
+CFLAGS?=$(COMMMON_FLAGS) --std=gnu11 $(C_OPT_FLAGS)
+CXXFLAGS?=$(COMMON_FLAGS) --std=gnu++20 $(CXX_OPT_FLAGS)
+LDFLAGS?=$(LD_OPT_FLAGS)
 
 DAYS= $(wildcard day*)
 
diff --git a/day3/Makefile b/day3/Makefile
new file mode 100644
index 0000000..e37a3a7
--- /dev/null
+++ b/day3/Makefile
@@ -0,0 +1,30 @@
+COMMON_OPT_FLAGS?= -O3 -march=native -pipe -flto \
+	 -march=native -fgraphite -fopenmp -floop-parallelize-all -ftree-parallelize-loops=4 \
+	 -floop-interchange -ftree-loop-distribution -floop-strip-mine -floop-block \
+	 -fno-stack-check -fno-strict-aliasing 
+
+C_OPT_FLAGS?=
+CXX_OPT_FLAGS?= -felide-constructors
+LD_OPT_FLAGS?=-O3 -flto
+
+COMMON_FLAGS=-Wall -pedantic $(COMMON_OPT_FLAGS)
+
+CFLAGS?=$(COMMMON_FLAGS) --std=gnu11 $(C_OPT_FLAGS)
+CXXFLAGS?=$(COMMON_FLAGS) --std=gnu++20 $(CXX_OPT_FLAGS)
+LDFLAGS?=$(LD_OPT_FLAGS)
+
+CXXFLAGS+= -fno-exceptions
+
+.PHONY: all
+all: part1 part2
+
+part1: day3.cpp
+	$(CXX) $< $(CXXFLAGS) -o $@ $(LDFLAGS)
+	strip $@
+
+part2: day3.cpp
+	$(CXX) $< -DPART2 $(CXXFLAGS) -o $@ $(LDFLAGS)
+	strip $@
+
+clean:
+	rm -f part{1,2}
diff --git a/day3/day3.cpp b/day3/day3.cpp
new file mode 100644
index 0000000..2d1ceaf
--- /dev/null
+++ b/day3/day3.cpp
@@ -0,0 +1,79 @@
+#include <vector>
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <tuple>
+
+using mod_table = std::vector<std::vector<bool> >;
+
+mod_table read_input(const char* _input)
+{
+	std::ifstream input(_input);
+	if(!input) {
+		std::cerr << "Failed to open file: " << _input << std::endl;
+		std::terminate();
+	}
+	mod_table output;
+
+	std::string str;
+	while(input)
+	{
+		if(!std::getline(input, str)) break;
+		std::vector<bool> ln(str.size());
+		int i=0;
+		for(const auto& chr : str)
+		{
+			switch(chr)
+			{
+			case '#': ln[i] = true;
+			default:  i++; break;
+			}
+		}
+		output.push_back(std::move(ln));
+		str.clear();
+	}
+	return output;
+}
+
+template<typename V>
+inline std::size_t wrapping_index(const V& vec, std::size_t i)
+{
+	return (i % vec.size());
+}
+
+std::size_t count_slope(const mod_table& table, std::size_t stepx, std::size_t stepy)
+{
+	std::size_t x=0;
+	std::size_t r=0;
+	for(std::size_t y=0;y<table.size();y+=stepy, x+=stepx)
+	{
+		r += table[y][wrapping_index(table[y], x)] ? 1 : 0;
+	}
+	return r;
+}
+
+int main()
+{
+	
+	const mod_table table = read_input("input");
+#ifdef PART2
+	const auto paths = {
+		std::tuple<std::size_t, std::size_t>(1, 1),
+		std::tuple<std::size_t, std::size_t>(3, 1),
+		std::tuple<std::size_t, std::size_t>(5, 1),
+		std::tuple<std::size_t, std::size_t>(7, 1),
+		std::tuple<std::size_t, std::size_t>(1, 2),
+	};
+
+	std::size_t r=1;
+	for(const auto& [x, y] : paths)
+	{
+		r*= count_slope(table, x, y);
+	}
+#else
+	auto r = count_slope(table, 3, 1); 
+#endif
+
+	std::cout << r << std::endl;
+	return 0;
+}