#include <iostream>
using namespace std;
 
string doSum(string a, string b);
 
int main()
{
    string result = doSum("1234567890", "123789456123");
    cout << result << "\n";
}
 
string doSum(string a, string b)
{
    if(a.size() < b.size())
        swap(a, b);
 
    int j = a.size()-1;
    for(int i=b.size()-1; i>=0; i--, j--)
        a[j]+=(b[i]-'0');
 
    for(int i=a.size()-1; i>0; i--)
        if(a[i] > '9')
        {
            int d = a[i]-'0';
            a[i-1] = ((a[i-1]-'0') + d/10) + '0';
            a[i] = (d%10)+'0';
        }
    if(a[0] > '9')
    {
        string k;
        k+=a[0];
        a[0] = ((a[0]-'0')%10)+'0';
        k[0] = ((k[0]-'0')/10)+'0';
        a = k+a;
    }
    return a;
}

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