species_1 + species_2 -> species_3 species_3 -> species_1 + species_2 species_3 -> species_2 + species_4 species_2 + species_4 -> species_5 species_5 -> species_2 + species_4 species_5 -> species_2 + species_6 species_13 + species_6 -> species_21 species_21 -> species_13 + species_6 species_21 -> species_13 + species_4 species_13 + species_4 -> species_22 species_22 -> species_13 + species_4 species_22 -> species_23 species_23 -> species_1 + species_13 species_1 + species_13 -> species_23 species_7 + species_8 -> species_9 species_9 -> species_7 + species_8 species_9 -> species_10 + species_8 species_10 + species_8 -> species_11 species_11 -> species_10 + species_8 species_11 -> species_2 + species_8 species_13 + species_2 -> species_12 species_12 -> species_13 + species_2 species_12 -> species_10 + species_13 species_10 + species_13 -> species_14 species_14 -> species_10 + species_13 species_14 -> species_15 species_15 -> species_13 + species_7 species_13 + species_7 -> species_15 species_16 + species_18 -> species_17 species_17 -> species_16 + species_18 species_17 -> species_18 + species_8 species_20 + species_8 -> species_19 species_19 -> species_20 + species_8 species_19 -> species_27 species_2 + species_20 -> species_24 species_24 -> species_2 + species_20 species_24 -> species_10 + species_20 species_10 + species_20 -> species_25 species_25 -> species_10 + species_20 species_25 -> species_26 species_26 -> species_20 + species_7 species_20 + species_7 -> species_26 species_27 -> species_16 + species_20 species_16 + species_20 -> species_27