diff --git a/app/main.py b/app/main.py
index 626f41cf..7460c789 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,34 +1,111 @@
+from typing import List, Tuple, Dict, Optional
+
+
 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: int = row
+        self.column: int = column
+        self.is_alive: bool = is_alive
 
 
 class Ship:
-    def __init__(self, start, end, is_drowned=False):
-        # Create decks and save them to a list `self.decks`
-        pass
+    def __init__(self, start: Tuple[int, int], end: Tuple[int, int]) -> None:
+        self.decks: List[Deck] = self._create_decks(start, end)
+        self.is_drowned: bool = False
 
-    def get_deck(self, row, column):
-        # Find the corresponding deck in the list
-        pass
+    def _create_decks(
+            self,
+            start: Tuple[int, int],
+            end: Tuple[int, int]
+    ) -> List[Deck]:
+        decks: List[Deck] = []
+        if start[0] == end[0]:  # Horizontal ship
+            for col in range(start[1], end[1] + 1):
+                decks.append(Deck(start[0], col))
+        elif start[1] == end[1]:  # Vertical ship
+            for row in range(start[0], end[0] + 1):
+                decks.append(Deck(row, start[1]))
+        return decks
 
-    def fire(self, row, column):
-        # Change the `is_alive` status of the deck
-        # And update the `is_drowned` value if it's needed
-        pass
+    def get_deck(self, row: int, column: int) -> Optional[Deck]:
+        for deck in self.decks:
+            if deck.row == row and deck.column == column:
+                return deck
+        return None
+
+    def fire(self, row: int, column: int) -> bool:
+        deck = self.get_deck(row, column)
+        if deck and deck.is_alive:
+            deck.is_alive = False
+            self.is_drowned = all(not d.is_alive for d in self.decks)
+            return True
+        return False
 
 
 class Battleship:
-    def __init__(self, ships):
-        # 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
-
-    def fire(self, location: tuple):
-        # 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
+    def __init__(
+            self,
+            ships: List[Tuple[Tuple[int, int], Tuple[int, int]]]
+    ) -> None:
+        self.ships: List[Ship] = [Ship(start, end) for start, end in ships]
+        self.field: Dict[Tuple[int, int], Ship] = {}
+        self._initialize_field()
+        self._validate_field()
+
+    def _initialize_field(self) -> None:
+        for ship in self.ships:
+            for deck in ship.decks:
+                self.field[(deck.row, deck.column)] = ship
+
+    def fire(self, location: Tuple[int, int]) -> str:
+        if location not in self.field:
+            return "Miss!"
+
+        ship = self.field[location]
+        hit = ship.fire(*location)
+        if hit:
+            return "Sunk!" if ship.is_drowned else "Hit!"
+        return "Miss!"
+
+    def print_field(self) -> None:
+        field: List[List[str]] = [["~" for _ in range(10)] for _ in range(10)]
+        for (row, col), ship in self.field.items():
+            deck = ship.get_deck(row, col)
+            if deck.is_alive:
+                field[row][col] = "□"  # Alive deck
+            elif ship.is_drowned:
+                field[row][col] = "x"  # Drowned deck
+            else:
+                field[row][col] = "*"  # Hit deck of alive ship
+
+        for row in field:
+            print(" ".join(row))
+
+    def _validate_field(self) -> None:
+        ship_lengths: List[int] = [len(ship.decks) for ship in self.ships]
+        if len(ship_lengths) != 10:
+            raise ValueError("There must be exactly 10 ships.")
+
+        counts: Dict[int, int] = {
+            1: 0,
+            2: 0,
+            3: 0,
+            4: 0
+        }
+
+        for length in ship_lengths:
+            if length > 4:
+                raise ValueError("Ship lengths cannot exceed 4.")
+            counts[length] += 1
+
+        if (counts[1] != 4 or counts[2] != 3
+                or counts[3] != 2 or counts[4] != 1):
+            raise ValueError("Invalid ship configuration.")
+
+        for ship in self.ships:
+            for deck in ship.decks:
+                for row in range(deck.row - 1, deck.row + 2):
+                    for col in range(deck.column - 1, deck.column + 2):
+                        if ((row, col) in self.field
+                                and self.field[(row, col)] != ship):
+                            raise ValueError("Ships cannot be adjacent.")