DECLARE FUNCTION add$ (X AS STRING, typS AS STRING, typF AS STRING)
CLS
DIM sym AS STRING
INPUT X$
lastend = LEN(X$)
FOR i = 1 TO LEN(X$)
        sym = MID$(X$, i, 1)
        IF sym <> "(" AND sym <> ")" AND sym <> "[" AND sym <> "]" THEN
                X$ = "NO"
                PRINT X$
                SYSTEM
        END IF
NEXT i
FOR i = 1 TO LEN(X%) - 1
        IF MID$(X$, i, 2) = "(]" OR MID$(X$, i, 2) = "[)" THEN
                X$ = "NO"
                PRINT X$
                SYSTEM
        END IF
NEXT i
LENX = LEN(X$)
FOR n = 1 TO LEN(X$)
        sym$ = RIGHT$(X$, n)
        first$ = LEFT$(sym$, 1)
        IF first$ = "(" THEN
                k = 0
                FOR i = n TO LEN(X$)
                        IF MID$(sym$, n, 1) = "(" THEN k = k + 1
                        IF MID$(sym$, n, 1) = ")" THEN k = k - 1
                        IF k > 0 THEN X$ = X$ + STRING$(k, ")")
                NEXT i
        ELSEIF first$ = "[" THEN
                k = 0
                FOR i = n TO LEN(X$)
                        IF MID$(sym$, n, 1) = "[" THEN k = k + 1
                        IF MID$(sym$, n, 1) = "]" THEN k = k - 1
                        IF k > 0 THEN X$ = X$ + STRING$(k, "]")
                NEXT i
        END IF
NEXT n
PRINT X$
SYSTEM