set(binary_resolution).
clear(print_initial_clauses).
clear(print_kept).
clear(print_given).
assign(max_seconds,1).
assign(stats,none).

formulas(sos).
-S11.   -B11.
-S21.   B21.
S12.    -B12.
S11 | -W11.     S11 | -W12.     S11 | -W21.
S21 | -W11.     S21 | -W21.     S21 | -W22.     S21 | -W31.
S12 | -W11.     S12 | -W12.     S12 | -W22.     S12 | -W13.
-S12 | W11 | W12 | W22 | W13. 
end_of_list.

formulas(goals).
W13.
end_of_list.