When  гн(иј)ездо / gn(ij)ezdo is the serbo-croatian how many proto-slavics are there?
create table table_26757_4 (proto_slavic varchar, serbo_croatian varchar, PRIMARY KEY (proto_slavic))
select count(proto_slavic) from table_26757_4 where serbo_croatian = "гн(иј)ездо / gn(ij)ezdo"