.sql

create table Edges (n0 INTEGER, n1 INTEGER, label TEXT);
insert into Edges (n0, n1, label) values (0, 1, "e1");
insert into Edges (n0, n1, label) values (1, 2, "e2");
insert into Edges (n0, n1, label) values (1, 3, "e3");
insert into Edges (n0, n1, label) values (2, 4, "e4");
insert into Edges (n0, n1, label) values (3, 5, "e5");

with recursive Traverse(n0, n1)
as   ( values(0,0) UNION
       select E1.n0, E2.n1
       from Traverse E1, Edges E2
       where E1.n1 = E2.n0
     )   
     select E.n1 from Traverse E order by E.n1 desc limit 1;