Please help?

[ZaurBilalov]

Can you help me to find sum of like this numbers ? 10¹⁰⁰+10¹⁰⁰
I make like that program : (But it can't find negative answer :( )

// abs(max)-abs(min)=x
#include  <iostream>
#include  <string>
#include  <algorithm>
using namespace std;
int main()
{
    string a, b;
    cin>>a>>b;
    
    reverse(a.begin(), a.end());
    reverse(b.begin(), b.end());

    
    
    for(int z=0; z<a.length(); z++)
        a[z]-=48;
    for(int z=0; z<b.length(); z++)
        b[z]-=48;
    
    for(int z=0; z<b.length(); z++){
       a[z]+=b[z];
        if(a[z] > 9){
            if (z == b.length()-1){
                a+=a[z]/10;
                a[z]%=10;
            }
            else
                a[z+1] += a[z]/10,
                a[z] = a[z]%10;
        }
    }
    for(int g=b.length(); g<a.length(); g++){
      if (a[g] > 9)
          a[g+1]+= a[g]/10,
          a[g]%=10;
    }
    
    
    if(a[a.length()-1] > 9){
        a+=a[a.length()-1]/10;
        a[a.length()-2] %= 10;}
   
    reverse(a.begin(), a.end());
    for(int z=0; z<a.length(); z++){
        cout<<int(a[z]);
    }
    cout<<endl;
    
    
    
    return 0;
}