| #f2 #I #L1 #L2 #_ #IHL #J #K #H elim (IHL … H) -IHL
/3 width=7 by after_next, ex3_2_intro, drops_drop/
| #f2 #I1 #I2 #L1 #L2 #HL #_ #_ #J #K #H destruct
| #f2 #I #L1 #L2 #_ #IHL #J #K #H elim (IHL … H) -IHL
/3 width=7 by after_next, ex3_2_intro, drops_drop/
| #f2 #I1 #I2 #L1 #L2 #HL #_ #_ #J #K #H destruct