Длинная арифметика. Требуется сложить два целых числа А и В

INPUT "input n: ", n
INPUT "input m: ", m
ns$ = inic$(n)
ms$ = inic$(m)
res$ = add$(ns$, ms$)
FOR i = LEN(res$) TO 1 STEP -1
    PRINT MID$(res$, i, 1);
NEXT
 
FUNCTION inic$ (v)
buf$ = LTRIM$(STR$(v))
i = 1
j = LEN(buf$)
WHILE i < j
    t$ = MID$(buf$, i, 1)
    MID$(buf$, i, 1) = MID$(buf$, j, 1)
    MID$(buf$, j, 1) = t$
    i = i + 1
    j = j - 1
WEND
inic$ = buf$
END FUNCTION
 
FUNCTION max (lhs, rhs)
IF rhs > lhs THEN max = rhs ELSE max = lhs
END FUNCTION
 
FUNCTION add$ (lhs$, rhs$)
i = 1
ret$ = STRING$(LEN(lhs$ + rhs$) + 1, "0")
WHILE i <= max(LEN(lhs$), LEN(rhs$)) OR carry
    IF i <= LEN(lhs$) THEN a = VAL(MID$(lhs$, i, 1)) ELSE a = 0
    IF i <= LEN(rhs$) THEN b = VAL(MID$(rhs$, i, 1)) ELSE b = 0
    cur = a + b + carry
    MID$(ret$, i, 1) = inic$(cur MOD 10)
    carry = cur \ 10
    i = i + 1
WEND
add$ = del$(ret$)
END FUNCTION
 
FUNCTION del$ (ret$)
FOR i = LEN(ret$) TO 1 STEP -1
    IF MID$(ret$, i, 1) <> "0" OR LEN(buf$) <> 0 OR i = 1 THEN
        buf$ = MID$(ret$, i, 1) + buf$
    END IF
NEXT
del$ = buf$
END FUNCTION

INPUT "input a: ", sa$
INPUT "input b: ", sb$
WHILE carry OR i < LEN(sa$) OR i < LEN(sb$)
    IF i < LEN(sa$) THEN a = VAL(MID$(sa$, LEN(sa$) - i, 1)) ELSE a = 0
    IF i < LEN(sb$) THEN b = VAL(MID$(sb$, LEN(sb$) - i, 1)) ELSE b = 0
    cur = a + b + carry
    ret$ = LTRIM$(STR$(cur MOD 10)) + ret$
    carry = cur \ 10
    i = i + 1
WEND
PRINT ret$

CLS
DIM a AS STRING
DIM b AS STRING
DIM c AS STRING
DIM d AS INTEGER
 
INPUT "A ="; a
INPUT "B ="; b
CLS
IF LEN(a) > LEN(b) THEN
   k = LEN(a)
   b = STRING$(k - LEN(b), " ") + b
ELSE
   k = LEN(b)
   a = STRING$(k - LEN(a), " ") + a
END IF
 
LOCATE 2, 60 - LEN(a)
PRINT a
LOCATE 3, 58 - LEN(a)
PRINT "+"
LOCATE 4, 60 - LEN(b)
PRINT b
LOCATE 5, 60 - k
PRINT STRING$(k, "-")
 
d = 0
 
FOR i = k TO 1 STEP -1
   a1 = VAL(MID$(a, i, 1))
   b1 = VAL(MID$(b, i, 1))
   c1 = a1 + b1 + d
   d = 0
   IF c1 > 9 THEN
      d = 1
      c1 = c1 - 10
   END IF
   c = LTRIM$(STR$(c1)) + c
NEXT i
   IF d THEN c = "1" + c
LOCATE 6, 60 - k
PRINT c
END