Найти произведение положительных элементов массива A(N,M) — QBasic(Бейсик)

INPUT "vvedite kolichestvo strok N ", n
INPUT "vvedite kolichestvo stolbcov M ", m
DIM a(n, m)
FOR i = 1 TO n
    FOR j = 1 TO m
        INPUT "vvedite element ", a(i, j)
    NEXT
NEXT
FOR i = 1 TO n
    FOR j = 1 TO m
        PRINT a(i, j);
    NEXT
    PRINT
NEXT
p = 1
FOR i = 1 TO n
    FOR j = 1 TO m
        IF a(i, j) > 0 THEN p = p * a(i, j)
    NEXT
    PRINT
NEXT
PRINT "proizvedenie="; p