CREATE OR REPLACE FUNCTION max_population() RETURNS <ENTER> AS 

$$

DECLARE
   popul <ENTER>;
   maxpop <ENTER>;
   c_pop CURSOR FOR <ENTER>;

BEGIN
 maxpop = 0;
 OPEN c_pop;
  LOOP 
  FETCH c_pop INTO popul;
    EXIT WHEN NOT FOUND; 
  maxpop = <ENTER>;
  END LOOP; 
 CLOSE c_pop; 
 RETURN maxpop;
END;
$$

LANGUAGE 'plpgsql';