diff --git a/src/fib.erl b/src/fib.erl
index 20e8176..92efb40 100644
--- a/src/fib.erl
+++ b/src/fib.erl
@@ -1,5 +1,5 @@
 -module(fib).
--export([fib_p/1]).
+-export([fib_p/1, fib_g/1, tail_fib/1, say/0, start_time_check/0]).
 
 % Сопоставление с образцом
 fib_p(0) -> 0;
@@ -9,4 +9,24 @@ fib_p(N) -> fib_p(N - 1) + fib_p(N - 2).
 % Сторожевая последовательность
 fib_g(N) when N < 1 -> 0;
 fib_g(N) when N < 2 -> 1;
-fib_g(N) -> fib_g(N-1) + fib_g(N-2).
+fib_g(N) -> fib_g(N - 1) + fib_g(N - 2).
+
+% Хвостовая рекурсия
+tail_fib(N) -> tfib(N, 0, 1).
+tfib(0, Result, Next) -> Result;
+tfib(N, Result, Next) -> tfib(N - 1, Next, Result + Next).
+
+say() -> io:format("The result is: ~p~n", [tail_fib(10)]).
+
+exec_time(Depth) ->
+  Start = os:timestamp(),
+  fib_p(Depth),
+  io:format("Depth = ~p, Time ~f sec~n", [Depth, (timer:now_diff(os:timestamp(), Start) / 1000)]).
+
+for(0, _, _) -> [];
+for(N, Term, Step) when N > 0 ->
+  exec_time(N),
+  [Term | for(N - Step, Term, Step)].
+
+start_time_check() ->
+  for(40, 20, 5).
diff --git a/test/fib_test.erl b/test/fib_test.erl
index 7fbcdc2..c3d8dca 100644
--- a/test/fib_test.erl
+++ b/test/fib_test.erl
@@ -11,7 +11,8 @@
 
 fib_test_() -> [
   {"Test fib_p", fun test_fib_p/0 },
-  {"Test fib_g", fun test_fib_g/0 }
+  {"Test fib_g", fun test_fib_g/0 },
+  {"Test tail_fib", fun test_tail_fib/0 }
 ].
 
 test_fib_p() ->
@@ -39,3 +40,16 @@ test_fib_g() ->
   ?assertEqual(21, fib:fib_g(8)),
   ?assertEqual(34, fib:fib_g(9)),
   ?assertEqual(55, fib:fib_g(10)).
+
+test_tail_fib() ->
+  ?assertEqual(0, fib:tail_fib(0)),
+  ?assertEqual(1, fib:tail_fib(1)),
+  ?assertEqual(1, fib:tail_fib(2)),
+  ?assertEqual(2, fib:tail_fib(3)),
+  ?assertEqual(3, fib:tail_fib(4)),
+  ?assertEqual(5, fib:tail_fib(5)),
+  ?assertEqual(8, fib:tail_fib(6)),
+  ?assertEqual(13, fib:tail_fib(7)),
+  ?assertEqual(21, fib:tail_fib(8)),
+  ?assertEqual(34, fib:tail_fib(9)),
+  ?assertEqual(55, fib:tail_fib(10)).