Выяснить, есть ли в массиве хотя бы одна пара совпадающих по величине чисел — Basic(Бейсик)

DIM a(4,4)
DATA  0,0,0,1,0,0,1,2,0,1,2,3,1,2,3,4
FOR i=1 TO 4
FOR j=1 TO 4
READ a(i,j)
NEXT
NEXT
FOR i=1 TO 4
FOR j=1 TO 4
PRINT a(i,j);" ";
NEXT
PRINT
NEXT
FOR i=1 TO 4
FOR j=1 TO 4
FOR k=1 TO 4
FOR l=1 TO 4
IF (i<>k)AND(j<>l)AND (a(i,j)=a(k,l)THEN f=1
NEXT
NEXT
NEXT
NEXT
IF f=1 THEN PRINT "yes"ELSE PRINT "no"