diff --git a/lib/cnf.cpp b/lib/cnf.cpp
new file mode 100644
index 0000000..6b5d9cf
--- /dev/null
+++ b/lib/cnf.cpp
@@ -0,0 +1,84 @@
+#include "cnf.hpp"
+
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <stdexcept>
+
+namespace fs = std::filesystem;
+
+const fs::path CNF_DIR = "./CNF";
+
+bool CNF::write_dimacs(const std::string& filename) const {
+    fs::create_directories(CNF_DIR);
+
+    fs::path path = CNF_DIR / filename;
+    path = path.lexically_normal();
+
+    std::ofstream out(path);
+    if (!out) {
+        std::cerr << "Error: Could not open file " << path << "\n";
+        return false;
+    }
+
+    out << "p cnf " << n << " " << clauses.size() << "\n";
+
+    for (const auto& cl : clauses) {
+        for (int lit : cl) {
+            out << lit << " ";
+        }
+        out << "0\n";
+    }
+
+    return true;
+}
+
+CNF CNF::read_dimacs(const std::string& filename) {
+    CNF f;
+
+    std::ifstream in(filename);
+    if (!in) {
+        throw std::runtime_error("Could not open DIMACS file.");
+    }
+
+    std::string line;
+    long expected_clauses = 0;
+
+    while (std::getline(in, line)) {
+        if (line.empty()) continue;
+
+        if (line[0] == 'c') continue;
+
+        if (line[0] == 'p') {
+            std::istringstream iss(line);
+            std::string tmp, format;
+            iss >> tmp >> format >> f.n >> expected_clauses;
+
+            if (format != "cnf") {
+                throw std::runtime_error("Unsupported DIMACS format.");
+            }
+            continue;
+        }
+
+        std::istringstream iss(line);
+        Clause cl;
+        int lit;
+
+        while (iss >> lit) {
+            if (lit == 0) break;
+            cl.push_back(lit);
+        }
+
+        if (!cl.empty()) {
+            f.clauses.push_back(cl);
+        }
+    }
+
+    if (expected_clauses != 0 &&
+        f.clauses.size() != (size_t)expected_clauses) {
+        std::cerr << "Warning: Clause count mismatch.\n";
+    }
+
+    return f;
+}
diff --git a/lib/cnf.hpp b/lib/cnf.hpp
new file mode 100644
index 0000000..7c4649e
--- /dev/null
+++ b/lib/cnf.hpp
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+using Clause = std::vector<int>;
+
+class CNF {
+public:
+    long n = 0;
+    std::vector<Clause> clauses;
+
+    virtual ~CNF() = default;
+
+    virtual bool write_dimacs(const std::string& filename) const;
+    static CNF read_dimacs(const std::string& filename);
+};
diff --git a/lib/kcnf.hpp b/lib/kcnf.hpp
index 915caaf..9a8f2c1 100644
--- a/lib/kcnf.hpp
+++ b/lib/kcnf.hpp
@@ -1,18 +1,13 @@
 #pragma once
 
-#include <string>
-#include <vector>
+#include "cnf.hpp"
 
-using Clause = std::vector<int>; // makes it nicer to read
-
-class KCNF {
+class KCNF : public CNF {
 public:
-    long n = 0;
     long k = 0;
-    std::vector<Clause> clauses;
 
     static KCNF generate_random(long n, long c, long k);
 
-    bool write_dimacs(const std::string& filename) const;
+    bool write_dimacs(const std::string& filename) const override;
     static KCNF read_dimacs(const std::string& filename);
 };