FUNCTION find(VAR a:ARRAY OF INTEGER; n,x:INTEGER): INTEGER;
VAR l,r,mid:INTEGER;
BEGIN
     mid:=(l+r) DIV 2;
     WHILE l<=r DO
     BEGIN
         IF a[mid]=x THEN
         BEGIN
             find:=x;
             exit;
         END;
         IF x<a[mid] THEN
             r:=mid-1
         ELSE
             l:=mid+1;
     END;
END;