diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index dd86497..35eb1dd 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -2,6 +2,5 @@
 <project version="4">
   <component name="VcsDirectoryMappings">
     <mapping directory="" vcs="Git" />
-    <mapping directory="$PROJECT_DIR$/etu_algo_labs" vcs="Git" />
   </component>
 </project>
\ No newline at end of file
diff --git a/Shunting Yard/solution.py b/Shunting Yard/solution.py
index 683e70e..facb0f4 100644
--- a/Shunting Yard/solution.py	
+++ b/Shunting Yard/solution.py	
@@ -1,3 +1,4 @@
+from algo.LineCheck import is_valid
 from algo.Queue import Queue
 from algo.Stack import Stack
 
@@ -12,6 +13,7 @@ def get_priority(elem):
         return {"+": 0, "-": 0, "*": 1, "/": 1, "^": 2}.get(elem, -1)
 
     def infix_to_postfix(self, line: str):
+        assert is_valid(line)
         for elem in line.split():
             if elem.isnumeric():
                 self.__queue.push(elem)
diff --git a/Shunting Yard/tests.py b/Shunting Yard/tests.py
index 8e61da5..c7fb64d 100644
--- a/Shunting Yard/tests.py	
+++ b/Shunting Yard/tests.py	
@@ -41,3 +41,9 @@ def test_algo(self):
 
         for expr, expected in test_cases:
             self.assertEqual(Solution().infix_to_postfix(expr), expected)
+
+    def test_invalid_string(self):
+        self.assertRaises(
+            AssertionError, Solution().infix_to_postfix, "(1 + ((2)) /) 52)"
+        )
+        self.assertRaises(AssertionError, Solution().infix_to_postfix, ")(")
diff --git a/algo/LineCheck.py b/algo/LineCheck.py
new file mode 100644
index 0000000..1866b30
--- /dev/null
+++ b/algo/LineCheck.py
@@ -0,0 +1,18 @@
+from .Stack import Stack
+
+
+def is_valid(bracket_sequence):
+    stack = Stack()
+    brackets_dict = {
+        "[": "]",
+        "{": "}",
+        "(": ")",
+    }
+    for bracket in bracket_sequence:
+        if bracket not in ("[", "{", "(", ")", "}", "]"):
+            continue
+        if bracket in brackets_dict:
+            stack.push(bracket)
+        elif len(stack) == 0 or bracket != brackets_dict[stack.pop()]:
+            return False
+    return len(stack) == 0
diff --git a/algo/tests.py b/algo/tests.py
index 0194ea3..a63f9d7 100644
--- a/algo/tests.py
+++ b/algo/tests.py
@@ -3,6 +3,8 @@
 from .Queue import Queue
 from .Stack import Stack
 
+# from .LineCheck import is_valid
+
 
 class TestQueue(unittest.TestCase):
     def setup(self):