// Task 2
let x1 = [ ('a',1); ('b',2); ('c',3); ('d',4) ; ('a', 2) ;  ] // (<масть>,<достоинство>)
let search A =
    A |> List.filter (fun (x,y) -> x='a') |> List.length

printf "%A\n" ("Задание 2")
printf "%d\n" (search x1)