diff --git a/day4/.gitignore b/day4/.gitignore
new file mode 100644
index 0000000..d163863
--- /dev/null
+++ b/day4/.gitignore
@@ -0,0 +1 @@
+build/
\ No newline at end of file
diff --git a/day4/meson.build b/day4/meson.build
new file mode 100644
index 0000000..02f48e1
--- /dev/null
+++ b/day4/meson.build
@@ -0,0 +1,14 @@
+project('aoc2015_day4', 'cpp',
+        version: '1.0',
+        default_options: ['cpp_std=c++17',
+                          'warning_level=3',
+                          'b_ndebug=if-release'])
+
+
+so1_src = ['so1.cpp']
+so2_src = ['so2.cpp']
+
+day4_libs = [dependency('nettle', required: true)]
+
+executable('so1', so1_src, dependencies: day4_libs)
+executable('so2', so2_src, dependencies: day4_libs)
diff --git a/day4/so1.cpp b/day4/so1.cpp
new file mode 100644
index 0000000..36e529b
--- /dev/null
+++ b/day4/so1.cpp
@@ -0,0 +1,39 @@
+#include <iterator>
+#include <string>
+#include <iostream>
+#include <nettle/md5.h>
+
+using namespace std;
+
+int main() {
+  string input;
+
+  cout << "Initializing" << endl << "Input: ";
+  cin >> input;
+
+  md5_ctx ctx;
+  md5_init(&ctx);
+
+  bool found = false;
+  unsigned long long n = 1;
+  while (!found) {
+    string data = input + to_string(n);
+    size_t len_total = data.length();
+    md5_update(&ctx, len_total, (uint8_t*) data.c_str());
+
+    uint8_t result[MD5_DIGEST_SIZE];
+    md5_digest(&ctx, MD5_DIGEST_SIZE, result);
+
+    bool has_non_zero = false;
+    if (result[0] || result[1] || (result[2] & 0xf0)) {
+      has_non_zero = true;
+    }
+
+    if(!has_non_zero) {
+      found = true;
+      cout << "Result: " << n << endl;
+    }
+
+    n++;
+  }
+}
diff --git a/day4/so2.cpp b/day4/so2.cpp
new file mode 100644
index 0000000..9c80988
--- /dev/null
+++ b/day4/so2.cpp
@@ -0,0 +1,39 @@
+#include <iostream>
+#include <iterator>
+#include <nettle/md5.h>
+#include <string>
+
+using namespace std;
+
+int main() {
+  string input;
+
+  cout << "Initializing" << endl << "Input: ";
+  cin >> input;
+
+  md5_ctx ctx;
+  md5_init(&ctx);
+
+  bool found = false;
+  unsigned long long n = 1;
+  while (!found) {
+    string data = input + to_string(n);
+    size_t len_total = data.length();
+    md5_update(&ctx, len_total, (uint8_t *)data.c_str());
+
+    uint8_t result[MD5_DIGEST_SIZE];
+    md5_digest(&ctx, MD5_DIGEST_SIZE, result);
+
+    bool has_non_zero = false;
+    if (result[0] || result[1] || result[2]) {
+      has_non_zero = true;
+    }
+
+    if (!has_non_zero) {
+      found = true;
+      cout << "Result: " << n << endl;
+    }
+
+    n++;
+  }
+}