[ #a #I #G2 #L2 #V2 #T2 #X #H elim (lpx_inv_pair1 … H) -H
#K2 #W2 #HLK2 #HVW2 #H destruct
/3 width=5 by cpx_pair_sn, fqu_bind_dx, ex3_2_intro/
-| #G #L1 #K1 #T1 #U1 #e #HLK1 #HTU1 #K2 #HK12
+| #G #L1 #K1 #T1 #U1 #m #HLK1 #HTU1 #K2 #HK12
elim (drop_lpx_trans … HLK1 … HK12) -HK12
/3 width=7 by fqu_drop, ex3_2_intro/
]
[ #I #G1 #L1 #V1 #X #H elim (lpx_inv_pair2 … H) -H
#K1 #W1 #HKL1 #HWV1 #H destruct elim (lift_total V1 0 1)
/4 width=7 by cpx_delta, fqu_drop, drop_drop, ex3_2_intro/
-| #G #L1 #K1 #T1 #U1 #e #HLK1 #HTU1 #L0 #HL01
+| #G #L1 #K1 #T1 #U1 #m #HLK1 #HTU1 #L0 #HL01
elim (lpx_drop_trans_O1 … HL01 … HLK1) -L1
/3 width=5 by fqu_drop, ex3_2_intro/
]