C++ solution:

std::string schoolAddition(const std::string& add0, const std::string& add1) {

std::vector<char> ret_vec;
int add0_idx = add0.size() - 1;
int add1_idx = add1.size() - 1;
int size = max(add0.size(), add1.size());
int carry = 0;
while (size > 0) {

    int n_0 = add0_idx < 0 ? 0 : add0[add0_idx] - '0';
    int n_1 = add1_idx < 0 ? 0 : add1[add1_idx] - '0';

    int ret = n_0 + n_1 + carry;
    carry = ret / 10;

    ret_vec.push_back('0' + (ret % 10));

    add0_idx--;
    add1_idx--;
    size--;
}

if (carry > 0) {
    ret_vec.push_back('0' + carry);
}

std::reverse(ret_vec.begin(), ret_vec.end());

return std::string(ret_vec.data(), ret_vec.size());

}

std::string schoolMultiplication(std::string num0, std::string num1) { int carry = 0;

int j_c = 0;
std::vector<std::string> rets;
for (int j = num1.size() - 1; j >= 0; j--) {

    std::vector<char> tmp_vec;
    int n_1 = num1[j] - '0';
    for (int i = num0.size() - 1; i >= 0; i--) {
        int n_0 = num0[i] - '0';

        int ret = n_0 * n_1 + carry;
        int put = ret % 10;
        tmp_vec.push_back('0' + put);
        carry = ret / 10;
    }

    if (carry) {
        tmp_vec.push_back('0' + carry);
        carry = 0;
    }
    std::reverse(tmp_vec.begin(), tmp_vec.end());

    for (int k = 0; k < j_c; k++) {
        tmp_vec.push_back('0');
    }

    j_c++;
    rets.push_back(std::string(tmp_vec.data(), tmp_vec.size()));
}

std::string final_num = rets[0];
for (int i = 1; i < rets.size(); i++) {
    final_num = schoolAddition(final_num, rets[i]);
}

return final_num;

}

void extraLongFactorials(int n) {

std::string factorial = std::to_string(n);
for (int i = n - 1; i > 1; --i) {
    factorial = schoolMultiplication(factorial, std::to_string(i));
}

printf("%s\n", factorial.c_str());

}