% https://open.kattis.com/problems/grassseed
% 1s
% 1.4 Easy

% Shorter version (318 chars).
% Andriy Zyevakov submitted a version of 215 chars. How?
main:-ri(Cost),ri(_),ra(Area),Total is Cost*Area,format('~10f~n',[Total]).
main.
ra(Total):-rs(S),ra(S,0,Total).
ra(end_of_file,L,L):-!.
ra(S,L0,L):-split_string(S," ", "", Ss),maplist(number_chars,[A,B],Ss),L1 is L0 + A*B,rs(S2),ra(S2,L1,L).
rs(S):-read_line_to_string(user_input,S).
ri(N):-rs(S),number_string(N,S).