Дано предложение A$, содержащее три слова из 4 букв. Поменять первое слово с третьим- QBasic(Бейсик)

CLS
INPUT "vvedate text"; a$
n = LEN(a$): q$ = " ": k = 1
FOR i = 1 TO n
    IF MID$(a$, i, 1) = q$ THEN k = k + 1
NEXT
DIM b(k), e(k - 1), d$(k)
FOR i = 1 TO n
    IF MID$(a$, i, 1) = q$ THEN r = r + 1: e(r) = i
NEXT
FOR i = 1 TO k
    SELECT CASE i
        CASE IS = 1
            d$(1) = MID$(a$, 1, e(1) - 1)
        CASE IS = k
            d$(k) = MID$(a$, e(r) + 1, n)
        CASE 2 TO (k - 1)
            d$(i) = MID$(a$, e(i - 1) + 1, e(i) - e(i - 1) - 1)
    END SELECT
NEXT
SWAP d$(1), d$(3)
FOR i = 1 TO k
    v$ = v$ + " " + d$(i)
NEXT
PRINT v$