diff --git a/app/main.py b/app/main.py
index 626f41cf..51ca7777 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,34 +1,151 @@
+from typing import Tuple, 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 = row
+        self.column = column
+        self.is_alive = 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],
+            is_drowned: bool = False
+    ) -> None:
+        self.decks = []
+        self.is_drowned = is_drowned
+
+        r1, c1 = start
+        r2, c2 = end
+
+        if r1 != r2 and c1 != c2:
+            raise ValueError("Ships must be horizontal or vertical, "
+                             "not diagonal or rectangular.")
+
+        if r1 == r2:
+            for c_var in range(min(c1, c2), max(c1, c2) + 1):
+                self.decks.append(Deck(r1, c_var))
+        else:
+            for r_var in range(min(r1, r2), max(r1, r2) + 1):
+                self.decks.append(Deck(r_var, c1))
+
+    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) -> None:
+        deck = self.get_deck(row, column)
 
-    def get_deck(self, row, column):
-        # Find the corresponding deck in the list
-        pass
+        if deck and deck.is_alive:
+            deck.is_alive = False
 
-    def fire(self, row, column):
-        # Change the `is_alive` status of the deck
-        # And update the `is_drowned` value if it's needed
-        pass
+            self.is_drowned = all(
+                not d.is_alive for d in self.decks
+            )
 
 
 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) -> None:
+        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 _validate_field(self) -> None:
+        if len(self.ships) != 10:
+            raise ValueError("The total number of the ships should be 10.")
+
+        sizes_count = {1: 0, 2: 0, 3: 0, 4: 0}
+
+        for ship in self.ships:
+            size = len(ship.decks)
+            if size not in sizes_count:
+                raise ValueError(f"Invalid ship size detected: {size}")
+
+            sizes_count[size] += 1
+
+            for deck in ship.decks:
+                if not (0 <= deck.row < 10 and 0 <= deck.column < 10):
+                    raise ValueError(f"Ship deck {(deck.row, deck.column)} "
+                                     f"is out of bounds.")
+
+                for dr in [-1, 0, 1]:
+                    for dc in [-1, 0, 1]:
+                        neighbor = (deck.row + dr, deck.column + dc)
+                        if (neighbor in self.field
+                                and self.field[neighbor] != ship):
+                            raise ValueError("Ships shouldn't be located "
+                                             "in the neighboring cells.")
+
+        expected_sizes = {1: 4, 2: 3, 3: 2, 4: 1}
+        if sizes_count != expected_sizes:
+            raise ValueError(f"Invalid distribution of ships. "
+                             f"Expected {expected_sizes}, "
+                             f"got {sizes_count}")
+
+    def fire(self, location: tuple) -> str:
+        if location not in self.field:
+            return "Miss!"
+
+        row, column = location
+        ship = self.field[location]
+
+        ship.fire(row, column)
+
+        if ship.is_drowned:
+            return "Sunk!"
+
+        return "Hit!"
+
+    def print_field(self) -> None:
+        for r_coords in range(10):
+            row_symbols = []
+            for c_coords in range(10):
+                if (r_coords, c_coords) in self.field:
+                    ship = self.field[(r_coords, c_coords)]
+                    deck = ship.get_deck(r_coords, c_coords)
+
+                    if ship.is_drowned:
+                        row_symbols.append("x")
+                    elif not deck.is_alive:
+                        row_symbols.append("*")
+                    else:
+                        row_symbols.append(u"\u25A1")  # □
+                else:
+                    row_symbols.append("~")
+
+            print("  ".join(row_symbols))
+
+
+if __name__ == "__main__":
+    battle_ship = Battleship(
+        ships=[
+            ((0, 0), (0, 3)),
+            ((0, 5), (0, 6)),
+            ((0, 8), (0, 9)),
+            ((2, 0), (4, 0)),
+            ((2, 4), (2, 6)),
+            ((2, 8), (2, 9)),
+            ((9, 9), (9, 9)),
+            ((7, 7), (7, 7)),
+            ((7, 9), (7, 9)),
+            ((9, 7), (9, 7)),
+        ]
+    )