longsum

@echo off
setlocal EnableDelayedExpansion
set Number1=%1
set Number2=%2
set /A length1=0
set /A length2=0
:l1
set /A length1=!length1!+1
if NOT "!Number1:~%length1%,1!" == "" goto :l1
:l2
set /A length2=!length2!+1
if NOT "!Number2:~%length2%,1!" == "" goto :l2
if !length1! == !length2! (
    set length=!length1!
) else (
    if !length1! LSS !length2! (
        set /A length=!length2!
        :m1
        set /A length1=!length1!+1
        set Number1=0!Number1!
        if !length1! LSS !length! goto :m1
    ) else (
        set /A length=!length1!
        :m2
        set /A length2=!length2!+1
        set Number2=0!Number2!
        if !length2! LSS !length! goto :m2
    )
)
set /A remainder=0
set /A curn=0
set /A length=!length!-1
set /A curn=!Number1:~%length%,1!+!Number2:~%length%,1!
set /A curn=!curn!+!remainder!
if !curn! LSS 10 (
    set ans=!curn!
    set /A remainder=0
) else (
    set ans=!curn:~2,1!
    set /A remainder=1
)
set /A length=!length!-1
if NOT !length! LSS 0 goto :start
:start
    set /A curn=!Number1:~%length%,1!+!Number2:~%length%,1!
    set /A curn=!curn!+!remainder!
    if !curn! LSS 10 (
        set ans=!curn!!ans!
        set /A remainder=0
    ) else (
        set curn=!curn:~1,1!
        set ans=!curn!!ans!
        set /A remainder=1
    )
    set /A length=!length!-1
    if NOT !length! LSS 0 goto :start
set fn=!ans:~0,1!
if "!fn!" == "0" set ans=!ans:~1!
endlocal & set ans=%ans%