diff --git a/inc/syntaxer.hpp b/inc/syntaxer.hpp
index 1cb0e85..a7e2401 100644
--- a/inc/syntaxer.hpp
+++ b/inc/syntaxer.hpp
@@ -6,8 +6,9 @@
 namespace Syntax
 {
 
-int check_syntax(std::vector<Expression::Token>& tv);
-void apply_corrections(std::vector<Expression::Token>& tv);
+void pre_process(std::vector<Expression::Token>& tv);
+int check_syntax(const std::vector<Expression::Token>& tv);
+void post_process(std::vector<Expression::Token>& tv);
 std::vector<Expression::Operation> build_op_vector(const std::vector<Expression::Token>& tv);
 Expression::TreeNode ov_to_tree(const std::vector<Expression::Token> tv, const std::vector<Expression::Operation>& ov);
 void print_op_tree(const std::vector<Expression::Token> tv, const std::vector<Expression::Operation>& ov);
diff --git a/src/main.cpp b/src/main.cpp
index 0038e29..7a3bfe1 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -10,12 +10,14 @@ int main(int argc, char **argv)
 
 	std::vector<Expression::Token> tv = Parser::tokenize_input(argv[1]);
 
+	Syntax::pre_process(tv);
+
 	if (Syntax::check_syntax(tv))
 	{
 		return 0;
 	}
 
-	Syntax::apply_corrections(tv);
+	Syntax::post_process(tv);
 
 	std::vector<Expression::Operation> ov = Syntax::build_op_vector(tv);
 
diff --git a/src/syntaxer.cpp b/src/syntaxer.cpp
index e2e75a2..56153bb 100644
--- a/src/syntaxer.cpp
+++ b/src/syntaxer.cpp
@@ -8,6 +8,8 @@
 
 namespace Syntax {
 
+static int add_bracket_to(std::vector<Expression::Token>& tv, const int location, const int direction);
+
 static void highlight_issue(const std::vector<Expression::Token>& tv, const int location)
 {
 	int start = location - 7 < 0 ? 0 : location - 7;
@@ -30,7 +32,62 @@ static void highlight_issue(const std::vector<Expression::Token>& tv, const int
 	std::cout << "\n";
 }
 
-int check_syntax(std::vector<Expression::Token>& tv)
+void pre_process(std::vector<Expression::Token>& tv)
+{
+	pr_debug("Pre-process: remove empty brackets");
+	for (int i = 0; i < tv.size() - 1; i++)
+	{
+		if (tv[i].t == Expression::Token::OPERATOR
+			&& tv[i].v.o == Expression::Token::OPA
+			&& tv[i+1].t == Expression::Token::OPERATOR
+			&& tv[i+1].v.o == Expression::Token::CPA)
+		{
+			std::vector<int> highlight;
+			highlight.emplace_back(i);
+			highlight.emplace_back(i+1);
+			Parser::print_math_vector(tv, highlight);
+
+			tv.erase(tv.begin() + i, tv.begin() + i + 2);
+			i--;
+		}
+	}
+
+	pr_debug("Pre-process: unary minus");
+	int change = 1;
+	while (change)
+	{
+		change = 0;
+
+		for (int i = 0; i < tv.size() - 2; i++)
+		{
+			if (tv[i].t == Expression::Token::OPERATOR
+				&& tv[i].v.o != Expression::Token::CPA
+				&& tv[i+1].t == Expression::Token::OPERATOR
+				&& tv[i+1].v.o == Expression::Token::SUB
+				&& (tv[i+2].t == Expression::Token::CONST
+					|| tv[i+2].t == Expression::Token::VAR
+					|| (tv[i+2].t == Expression::Token::OPERATOR
+						&& tv[i+2].v.o == Expression::Token::OPA)))
+			{
+				std::vector<int> highlight;
+
+				tv.insert(tv.begin() + i + 1, Expression::Token(0.0));
+				tv.insert(tv.begin() + i + 1, Expression::Token(Expression::Token::OPA));
+				highlight.emplace_back(add_bracket_to(tv, i + 3, 1));
+
+				highlight.emplace(highlight.begin(), i+2);
+				highlight.emplace(highlight.begin(), i+1);
+				Parser::print_math_vector(tv, highlight);
+
+				i += 4;
+
+				change++;
+			}
+		}
+	}
+}
+
+int check_syntax(const std::vector<Expression::Token>& tv)
 {
 	int problem_cnt = 0;
 
@@ -639,7 +696,7 @@ static void weight_operators(std::vector<int>& operator_weights, const std::vect
 	}
 }
 
-void apply_corrections(std::vector<Expression::Token>& tv)
+void post_process(std::vector<Expression::Token>& tv)
 {
 	pr_debug("Post processing:");
 	Parser::print_math_vector(tv);
diff --git a/src/test-cases.cpp b/src/test-cases.cpp
index b372e86..c499977 100644
--- a/src/test-cases.cpp
+++ b/src/test-cases.cpp
@@ -99,7 +99,7 @@ TEST(tree_proper_test_1)
 TEST(tree_proper_test_2)
 {
 	std::vector<Expression::Token> o = Parser::tokenize_input("(1**5 * (1-2-3-4-5-6-7-8))");
-	Syntax::apply_corrections(o);
+	Syntax::post_process(o);
 	std::vector<Expression::Operation> ov = Syntax::build_op_vector(o);
 
 	return 0;