diff --git a/src/executor.rs b/src/executor.rs
index 4c1febf..1a5fcf9 100644
--- a/src/executor.rs
+++ b/src/executor.rs
@@ -40,6 +40,39 @@ impl LispState {
 			}
 		});
 
+		add_function(&mut table, "sub", |x| {
+			if x.len() != 2 {
+				return vec![LispValue::Nil]
+			}
+
+			if let (LispValue::Integer(lhs), LispValue::Integer(rhs)) = (&x[0], &x[1]) {
+				return vec![LispValue::Integer(lhs - rhs)];
+			}
+			vec![LispValue::Nil]
+		});
+
+		add_function(&mut table, "mul", |x| {
+			if x.len() != 2 {
+				return vec![LispValue::Nil]
+			}
+
+			if let (LispValue::Integer(lhs), LispValue::Integer(rhs)) = (&x[0], &x[1]) {
+				return vec![LispValue::Integer(lhs * rhs)];
+			}
+			vec![LispValue::Nil]
+		});
+
+		add_function(&mut table, "div", |x| {
+			if x.len() != 2 {
+				return vec![LispValue::Nil]
+			}
+
+			if let (LispValue::Integer(lhs), LispValue::Integer(rhs)) = (&x[0], &x[1]) {
+				return vec![LispValue::Integer(lhs / rhs)];
+			}
+			vec![LispValue::Nil]
+		});
+
 		LispState {
 			table
 		}
diff --git a/src/main.rs b/src/main.rs
index 802ed59..3e1bf0c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,7 +17,6 @@ fn main() {
 			Vec::new()
 		}
 	};
-	println!("{:?}", tokens);
 	let instructions = parse(tokens);
 
 	let state = LispState::new();
diff --git a/src/parser.rs b/src/parser.rs
index 77d4745..4a903a1 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -112,7 +112,6 @@ fn parse_exp(tokens: Vec<Token>) -> Vec<OpCode> {
 				Token::CloseParen => {
 					panic!("Unexpected closing parenthesis");
 				},
-				_ => todo!()
 			}
 
 			i += 1;
diff --git a/src/test.lisp b/src/test.lisp
index d7318cb..bb4be9e 100644
--- a/src/test.lisp
+++ b/src/test.lisp
@@ -1,3 +1,3 @@
 ; This is a comment
 
-(print (add 1333 12423))
\ No newline at end of file
+(print (add 1 (mul (div 16 2) (mul 13 2))))
\ No newline at end of file
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 1236334..0ea24e1 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -107,7 +107,9 @@ impl Tokenizer {
 					tokens.push(Token::Integer(self.storage.iter().collect::<String>().parse().unwrap()));
 					self.storage.clear();
 				} else {
-					self.storage.push(char);
+					if char != '_' {
+						self.storage.push(char);
+					}
 					continue;
 				}
 			}
@@ -166,7 +168,9 @@ impl Tokenizer {
 					} else if c.is_numeric() || c == '_' {
 						self.reading_num = true;
 						self.storage.clear();
-						self.storage.push(c);
+						if c != '_' {
+							self.storage.push(c);
+						}
 						continue;
 					}
 				}