#include <bits/stdc++.h>

#include <cstddef>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
using namespace std;
const int N = 1005;

class Bigint
{
public:
    int data[N], length;

    Bigint()
    {
        length = 1;
        memset(data, 0, sizeof data);
    }

    void set(const char* num);
    void set(const int num);

    Bigint(const int);
    Bigint(const string);
    Bigint(const Bigint&);
    int operator[](int index) const { return data[index]; };

    Bigint& operator=(const Bigint&);
    Bigint  operator+(const Bigint&) const;
    Bigint  operator-(const Bigint&) const;
    Bigint  operator*(const Bigint&) const;
    Bigint  operator/(const int&) const;
    int     operator%(const int&) const;
    bool    operator<(const Bigint&) const;
    bool    operator<(const int& t) const;
    void    print() const;
};

Bigint::Bigint(const string str) { this->set(str.c_str()); }

void Bigint::set(const char* num)
{
    size_t l     = strlen(num);
    this->length = l;
    for (int i = 0; i < l; i++) {
        data[i] = num[l - i - 1] - '0';
    }
}

void Bigint::set(const int num) { this->set(to_string(num).data()); }

void Bigint::print() const
{
    for (int i = length - 1; i >= 0; i--) printf("%d", data[i]);
    printf("\n");
}

Bigint Bigint::operator+(const Bigint& b) const
{
    Bigint c;
    auto&  a    = *this;
    auto   mlen = max(a.length, b.length);
    for (int i = 0; i < mlen; i++) {
        c.data[i]     = a[i] + b[i];
        c.data[i + 1] = c.data[i] / 10;
        c.data[i] %= 10;
    }
    c.length = c[mlen] == 0 ? mlen : mlen + 1;
    return c;
}

int main()
{
    string as, bs;
    cin >> as >> bs;
    Bigint a(as), b(bs);

    auto c = a + b;
    c.print();
    return 0;
}

测试0 0等均通过