diff --git a/app/main.py b/app/main.py
index 626f41cf..4e81a73a 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,34 +1,121 @@
+from __future__ import annotations
+
+
 class Deck:
-    def __init__(self, row, column, is_alive=True):
-        pass
+    def __init__(self, row: int, column: int, is_alive: bool = True) -> None:
+        self.row = row
+        self.column = column
+        self.is_alive = is_alive
+
+    def __repr__(self) -> str:
+        return f"Deck({self.row}, {self.column}, alive={self.is_alive})"
 
 
 class Ship:
-    def __init__(self, start, end, is_drowned=False):
+    def __init__(
+            self,
+            start: tuple[int, int],
+            end: tuple[int, int],
+            is_drowned: bool = False
+    ) -> None:
         # Create decks and save them to a list `self.decks`
-        pass
+        self.start = start
+        self.end = end
+        self.is_drowned = is_drowned
+        self.decks = []
 
-    def get_deck(self, row, column):
+        if start[0] == end[0]:
+            for i in range(start[1], end[1] + 1):
+                self.decks.append(Deck(start[0], i))
+        elif start[1] == end[1]:
+            for i in range(start[0], end[0] + 1):
+                self.decks.append(Deck(i, start[1]))
+
+    def get_deck(self, row: int, column: int) -> Deck | None:
         # Find the corresponding deck in the list
-        pass
+        for deck in self.decks:
+            if deck.row == row and deck.column == column:
+                return deck
+        return None
 
-    def fire(self, row, column):
+    def fire(self, row: int, column: int) -> str:
         # Change the `is_alive` status of the deck
         # And update the `is_drowned` value if it's needed
-        pass
+        deck = self.get_deck(row, column)
+        if deck:
+            deck.is_alive = False
+            if all(not _.is_alive for _ in self.decks):
+                self.is_drowned = True
+                return "Sunk!"
+            else:
+                return "Hit!"
+        return "Miss!"
 
 
 class Battleship:
-    def __init__(self, ships):
+    def __init__(
+            self,
+            ships: list[tuple[tuple[int, int], tuple[int, int]]]
+    ) -> None:
         # Create a dict `self.field`.
         # Its keys are tuples - the coordinates of the non-empty cells,
         # A value for each cell is a reference to the ship
         # which is located in it
-        pass
+        self.field = {}
+        self.ships = []
+
+        for start, end in ships:
+            ship = Ship(start, end)
+            self.ships.append(ship)
+            for deck in ship.decks:
+                self.field[(deck.row, deck.column)] = ship
+
+        self._validate_field()
 
-    def fire(self, location: tuple):
+    def fire(self, location: tuple[int, int]) -> str:
         # This function should check whether the location
         # is a key in the `self.field`
         # If it is, then it should check if this cell is the last alive
         # in the ship or not.
-        pass
+        if location in self.field:
+            ship = self.field[location]
+            result = ship.fire(location[0], location[1])
+            return result
+        return "Miss!"
+
+    def print_field(self) -> None:
+        field = [["~"] * 10 for _ in range(10)]
+        for ship in self.ships:
+            for deck in ship.decks:
+                if deck.is_alive:
+                    field[deck.row][deck.column] = "□"
+                else:
+                    field[deck.row][deck.column] = "*" if not ship.is_drowned \
+                        else "x"
+
+        for row in field:
+            print(" ".join(row))
+
+    def _validate_field(self) -> None:
+        if len(self.ships) == 10:
+            ships_count = {1: 0, 2: 0, 3: 0, 4: 0}
+
+            for ship in self.ships:
+                decks_count = len(ship.decks)
+                if decks_count in ships_count:
+                    ships_count[decks_count] += 1
+
+            if ships_count != {1: 4, 2: 3, 3: 2, 4: 1}:
+                raise ValueError("Invalid deck count.")
+        else:
+            raise ValueError("Should be 10 ships.")
+        for ship in self.ships:
+            for deck in ship.decks:
+                for row_offset in range(-1, 2):
+                    for col_offset in range(-1, 2):
+                        neighbor = (deck.row
+                                    + row_offset, deck.column + col_offset)
+                        if (neighbor in self.field
+                                and self.field[neighbor] != ship):
+                            raise ValueError("Ships should not be placed "
+                                             "in neighboring cells.")