diff --git a/res/2016/day12/test_input.txt b/res/2016/day12/test_input.txt
index e69de29..01a004b 100644
--- a/res/2016/day12/test_input.txt
+++ b/res/2016/day12/test_input.txt
@@ -0,0 +1,6 @@
+cpy 41 a
+inc a
+inc a
+dec a
+jnz a 2
+dec a
diff --git a/src/2016/Day12.cpp b/src/2016/Day12.cpp
index 6efed7b..7b6c126 100644
--- a/src/2016/Day12.cpp
+++ b/src/2016/Day12.cpp
@@ -2,30 +2,115 @@
 
 namespace y2016::day12
 {
-  REGISTER_DAY(2016, Day12, std::vector<int>, int);
+  enum class Operator
+  {
+    Cpy,
+    Inc,
+    Dec,
+    Jnz
+  };
 
-  REGISTER_TEST_EXAMPLE(2016, Day12, ExampleInput, 1, 0);
-  REGISTER_TEST(2016, Day12, Input, 1, 0);
-  REGISTER_TEST_EXAMPLE(2016, Day12, ExampleInput, 2, 0);
-  REGISTER_TEST(2016, Day12, Input, 2, 0);
+  struct Instruction
+  {
+    Operator op;
+    std::variant<char, int> arg1;
+    std::variant<char, int> arg2;
+  };
+
+  REGISTER_DAY(2016, Day12, std::vector<Instruction>, int);
+
+  REGISTER_TEST_EXAMPLE(2016, Day12, ExampleInput, 1, 42);
+  REGISTER_TEST(2016, Day12, Input, 1, 318007);
+  REGISTER_TEST_EXAMPLE(2016, Day12, ExampleInput, 2, 42);
+  REGISTER_TEST(2016, Day12, Input, 2, 9227661);
 
   READ_INPUT(input)
   {
-    std::vector<int> vec;
+    std::vector<Instruction> vec;
     std::string str;
     while (getline(input, str))
     {
+      Instruction instruction;
+      if (str[0] == 'c')
+      {
+        instruction.op = Operator::Cpy;
+        if (str[4] >= 'a' && str[4] <= 'd')
+          instruction.arg1 = str[4];
+        else
+          instruction.arg1 = (int)std::atoi(str.c_str() + 4);
+        instruction.arg2 = str[str.size() - 1];
+      }
+      else if (str[0] == 'i')
+      {
+        instruction.op = Operator::Inc;
+        instruction.arg1 = str[4];
+      }
+      else if (str[0] == 'd')
+      {
+        instruction.op = Operator::Dec;
+        instruction.arg1 = str[4];
+      }
+      else if (str[0] == 'j')
+      {
+        instruction.op = Operator::Jnz;
+        if (str[4] >= 'a' && str[4] <= 'd')
+          instruction.arg1 = str[4];
+        else
+          instruction.arg1 = (int)std::atoi(str.c_str() + 4);
+        instruction.arg2 = atoi(str.c_str() + 6);
+      }
+      vec.emplace_back(instruction);
     }
     return vec;
   }
 
+  int Run(const std::vector<Instruction>& instructions, std::vector<int> registers)
+  {
+    size_t pc = 0;
+    while (pc < instructions.size())
+    {
+      switch (instructions[pc].op)
+      {
+        case Operator::Cpy:
+        {
+          int number = 0;
+          if (std::holds_alternative<int>(instructions[pc].arg1))
+            number = std::get<int>(instructions[pc].arg1);
+          else
+            number = registers[std::get<char>(instructions[pc].arg1) - 'a'];
+          registers[std::get<char>(instructions[pc].arg2) - 'a'] = number;
+          break;
+        }
+        case Operator::Inc:
+          registers[std::get<char>(instructions[pc].arg1) - 'a']++;
+          break;
+        case Operator::Dec:
+          registers[std::get<char>(instructions[pc].arg1) - 'a']--;
+          break;
+        case Operator::Jnz:
+          int value = 0;
+          if (std::holds_alternative<int>(instructions[pc].arg1))
+            value = std::get<int>(instructions[pc].arg1);
+          else
+            value = registers[std::get<char>(instructions[pc].arg1) - 'a'];
+          if (value != 0)
+            pc += std::get<int>(instructions[pc].arg2) - 1;
+          break;
+      }
+      pc++;
+    }
+    return registers[0];
+  }
+
   OUTPUT1(input)
   {
-    return 0;
+    return Run(input, std::vector<int>(4));
   }
 
   OUTPUT2(input)
   {
-    return 0;
+    std::vector<int> registers(4);
+    registers[2] = 1;
+    return Run(input, registers);
   }
 }