Выяснить, есть ли в массиве хотя бы одна пара совпадающих по величине чисел. 4х4 0001001201231234 — QBasic(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"