mulU

#!/bin/bash
length () {
    length=0
    while [[ "${Num1:$length:1}" != "" ]]; do
        let "length=$length+1"; 2>nul
    done;
    echo $length
}
sum () {
    Num1=$1
    Num2=$2
    len1=$(length $Num1)
    len2=$(length $Num2)
    if [[ $len1 == $len2 ]]
    then
        len=$len1
    else
        if [[ $len1 > $len2 ]]
        then

            len=$len1
            while [[ $len2 != $len ]]; do
                Num2=0$Num2
                let "len2=$len2+1"
            done
        else
            len=$len2
            while [[ $len1 != $len ]]; do
                Num1=0$Num1
                let "len1=$len1+1"
            done
        fi
    fi
    rem=0
    let "len=$len-1"
    let "curn=${Num1:$len:1}+${Num2:$len:1}"
    if [[ ${curn:1:1} == "" ]]
    then
        ans=$curn
        rem=0
    else
        ans=${curn:1:1}
        rem=1
    fi
    while [[ $len > 0 ]]; do
        let "len=$len-1"
        let "curn=${Num1:$len:1}+${Num2:$len:1}+$rem"
        if [[ ${curn:1:1} == "" ]]
        then
            ans=$curn$ans
            rem=0
        else
            ans=${curn:1:1}$ans
            rem=1
        fi
    done
    echo $ans
}
n1=$1
n2=$2
l1=$(length $n1)
l2=$(length $n2)
cn2=0
ans=0
r=0
cz=0
let "l2=$l2-1"
cn2=${n2:l2:1}
let "cl1=$l1-1"
let "cm=${n1:$cl1:1}*$cn2"
let "cm=$cm+$r"
if [[ ${cm:1:1} == "" ]]
then
    ca=$cm
    r=0
else
    ca=${cm:1:1}
    r=${cm:0:1}
fi
let "cl1=$cl1=1"
while [[ $cl1 > 0 ]]; do
    let "cm=${n1:cl1:1}*$cn2"
    let "cm=$cm+$r"
    if [[ ${cm:1:1} == "" ]]
    then
        ca=$cm$ca
        r=0
    else
        ca=${cm:1:1}$ca
        r=${cm:0:1}
    fi
    let "cl1=$cl1-1"
done


if %remainder% GTR 0 (
    set curans=%remainder%%curans%
    set /A remainder=0
)
set ans=%curans%
set /A length2=%length2%-1
if %length2% LSS 0 goto :qw


:start
    set curn2=!Number2:~%length2%,1!
    set /A curlength1=!length1!-1
    set /A curm=!Number1:~%curlength1%,1!*!curn2!
    set /A curm=!curm!+%remainder%
    if %curm% LSS 10 (
        set curans=%curm%
        set /A remainder=0
    ) else (
        set curans=%curm:~1,1%
        set /A remainder=%curm:~0,1%
    )
    set /A curlength1=!curlength1!-1
    if %curlength1% LSS 0 goto :q1
    :m1
        set /A curm=!Number1:~%curlength1%,1!*!curn2!
        set /A curm=!curm!+%remainder%
        if %curm% LSS 10 (
            set curans=%curm%%curans%
            set /A remainder=0
        ) else (
            set curans=%curm:~1,1%%curans%
            set /A remainder=%curm:~0,1%
        )
        set /A curlength1=!curlength1!-1
        if not %curlength1% LSS 0 goto :m1
    :q1
    set curans=%curans%%curzerro%
    if %remainder% GTR 0 (
        set curans=%remainder%%curans%
        set /A remainder=0
    )
    set curzerro=%curzerro%0
    set /A ans=%curans%+%ans%
    set /A length2=%length2%-1
    if not %length2% LSS 0 goto :start
:qw
echo %ans%

endlocal