% 2017 Round 1C, Problem A, in Picat, by Afa Zhou
% https://code.google.com/codejam/contest/3274486/dashboard
% Ample Syrup

import util.

main() =>
    T = readln().to_number(),
    foreach(I in 1..T)
        initialize_table,
        [N, K] = [X.to_number() : X in readln().split()],
        Cakes = [[X.to_number() : X in readln().split()] : _ in 1..N].sort_down(),
        pick(Cakes,(K,K),S),
        printf(stderr, "Case #%d: %f\n", I, S)
    end.

% NOTE: it's special to select the bottom cake
table (+,+,max)
pick(_,0,S)  => S = 0.
pick([[R,H]|Cakes],(K,K),S) ?=>
    pick(Cakes,K-1,S1),
    S = S1+pi()*R*R+2*pi()*R*H.
pick([_|Cakes],KK@(K,K),S) =>
    pick(Cakes,KK,S).
pick([[R,H]|Cakes],K,S), K >= 1 ?=>
    pick(Cakes,K-1,S1),
    S = S1+2*pi()*R*H.
pick([_|Cakes],K,S), K >= 1 =>
    pick(Cakes,K,S).

picat-lang.org