diff --git a/.gitignore b/.gitignore
index e612e3c..51b9afa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -365,3 +365,5 @@ FodyWeavers.xsd
 /include
 /src
 *.json
+*.txt
+/build
diff --git a/Canvas.cpp b/Canvas.cpp
index 6d42e04..b01ae0b 100644
--- a/Canvas.cpp
+++ b/Canvas.cpp
@@ -9,6 +9,12 @@ void Canvas::changeMode(Mode _mode)
 	mode = _mode;
 }
 
+template <typename T, typename A, typename B>
+T makeOrderedPair(A* obj1, B* obj2)
+{
+	return (obj1->get_tag() < obj2->get_tag()) ? std::make_pair(obj1, obj2) : std::make_pair(obj2, obj1);
+}
+
 // TODO
 Line* Canvas::findAt(QPointF& pos)
 {
@@ -22,26 +28,41 @@ Line* Canvas::findAt(QPointF& pos)
 
 Point* Canvas::findPointAt(QPointF pos, qreal tolerance)
 {
+	Point* temp = nullptr;
 	for (Line* line : lines) {
 		QPointF p1(*line->p1.x, *line->p1.y);
 		QPointF p2(*line->p2.x, *line->p2.y);
 
 		if (dist_P2P(p1, pos) <= tolerance)
-			return &line->p1;
+			temp = &line->p1;
 		else if (dist_P2P(p2, pos) <= tolerance)
-			return &line->p2;
+			temp = &line->p2;
 	}
-	return nullptr;
+	return temp;
 }
 
-LinePair Canvas::makeOrderedPair(Line* l1, Line* l2)
+bool Canvas::areCoincident(Point* p1, Point* p2, bool mode)
 {
-	return (l1 < l2) ? std::make_pair(l1, l2) : std::make_pair(l2, l1);
+	int tag_0 = p1->get_tag(), tag_1 = p2->get_tag();
+	if (!mode){
+		return (tag_0 != tag_1 && *p1 == *p2);
+	}
+	else {
+		for (PointPair pair : P2Ppairs) {
+			int pair_tag_0 = pair.first->get_tag();
+			int pair_tag_1 = pair.second->get_tag();
+			if (pair_tag_0 == tag_0 && pair_tag_1 == tag_1 ||
+				pair_tag_0 == tag_1 && pair_tag_1 == tag_0)
+				return true;
+		}
+		return false;
+	}
+	
 }
 
 bool Canvas::areAlreadyParallel(Line* l1, Line* l2)
 {
-	return parallelPairs.count(makeOrderedPair(l1, l2)) > 0;
+	return parallelPairs.count(makeOrderedPair<LinePair>(l1, l2)) > 0;
 }
 
 void Canvas::mousePressEvent(QMouseEvent* event)
@@ -138,7 +159,7 @@ void Canvas::mousePressEvent(QMouseEvent* event)
 
 		if (!areAlreadyParallel(found, current_line)) {
 			sys.addConstraintParallel(*found, *current_line, constraints_count++);
-			parallelPairs.insert(makeOrderedPair(found, current_line));
+			parallelPairs.insert(makeOrderedPair<LinePair>(found, current_line));
 			current_line = nullptr;
 			update();
 			mode = Mode::None;
@@ -164,7 +185,6 @@ void Canvas::mousePressEvent(QMouseEvent* event)
 
 	else if (mode == Mode::Coincedent) {
 		Point* clickedPoint = findPointAt(scene);
-
 		if (!clickedPoint) {
 			firstPoint = nullptr;
 			update();
@@ -189,14 +209,17 @@ void Canvas::mousePressEvent(QMouseEvent* event)
 			if (&l->p1 == clickedPoint || &l->p2 == clickedPoint) l2 = l;
 		}
 
-		if (l1 == l2) {
+		if (l1 == l2 ||
+			(areCoincident(firstPoint, clickedPoint, true))) 
+		{
 			QMessageBox::warning(this, QString("NO!"), QString("P2P failed"));
 			firstPoint = nullptr;
 			update();
 			return;
 		}
 
-		sys.addConstraintP2PCoincident(*firstPoint, *clickedPoint, constraints_count++);
+		sys.addConstraintP2PCoincident(*clickedPoint, *firstPoint, constraints_count++);
+		P2Ppairs.insert(makeOrderedPair<PointPair>(clickedPoint, firstPoint));
 		firstPoint = nullptr;
 		mode = Mode::None;
 		after_constraint = true;
@@ -313,6 +336,8 @@ Canvas::~Canvas()
 	lines.clear();
 	params.clear();
 	points.clear();
+	parallelPairs.clear();
+	P2Ppairs.clear();
 
 	if (current_line) 
 		delete current_line;
diff --git a/Canvas.h b/Canvas.h
index 330d47f..d750778 100644
--- a/Canvas.h
+++ b/Canvas.h
@@ -24,6 +24,7 @@ enum class Mode : int
 
 // Удобный тип для хранения пары параллельных линий (порядок не важен)
 using LinePair = std::pair<Line*, Line*>;
+using PointPair = std::pair<Point*, Point*>;
 
 // ===================================================================
 // Основной класс холста
@@ -49,9 +50,8 @@ private:
     // ====================== Поиск и выбор ======================
     Line* findAt(QPointF&);                    // ищет линию под курсором
     Point* findPointAt(QPointF, qreal tolerance = 10.0);
-
+    bool areCoincident(Point*, Point*, bool mode = false);
     // ====================== Параллельность ======================
-    LinePair makeOrderedPair(Line* l1, Line* l2);
     bool areAlreadyParallel(Line* l1, Line* l2);           // проверка на дубликат
 
     // ====================== Перемещение ======================
@@ -65,6 +65,7 @@ private:
     std::vector<double*> params;                  // все параметры, передаваемые в солвер
 
     std::set<LinePair> parallelPairs;           // уже запараллеленные пары (защита от дублей)
+    std::set<PointPair> P2Ppairs;
 
     Line* current_line{ nullptr };
     Point* firstPoint{ nullptr };
@@ -72,5 +73,5 @@ private:
     bool after_constraint{ false };
 
     int obj_count{ 0 };            // тег для новых объектов
-    int constraints_count{ 0 };    // тег для новых ограничений
+    int constraints_count{ 0 };   // тег для новых ограничений
 };
\ No newline at end of file
diff --git a/GCS/Geo.cpp b/GCS/Geo.cpp
index c3a7683..c8eae86 100644
--- a/GCS/Geo.cpp
+++ b/GCS/Geo.cpp
@@ -149,6 +149,11 @@ void Line::set_tag(int _tag) {
     p2.set_tag(_tag);
 }
 
+int Line::get_tag()
+{
+    return tag;
+}
+
 // TODO
 bool Line::contains(QPointF pos, qreal tol) const
 {
diff --git a/GCS/Geo.h b/GCS/Geo.h
index e49c1fb..4ca9c41 100644
--- a/GCS/Geo.h
+++ b/GCS/Geo.h
@@ -64,6 +64,10 @@ public:
     void set_tag(int _tag) {
         tag = _tag;
     }
+
+    int get_tag() {
+        return tag;
+    }
 };
 
 using VEC_P = std::vector<Point>;
@@ -227,6 +231,7 @@ public:
     Line* Copy() override;
 
     void set_tag(int);
+    int get_tag();
     bool contains(QPointF, qreal tol = 10.0) const;
 };