void extraLongFactorials(int n) {
    int factorial[1000]{0}, product{0}, digit{0}, carry{0}, length{1};
    factorial[0]=1;
    for (int i = 2; i <= n; ++i) {
        for (int j = 0; j < length; ++j) {
            product =  i * factorial[j] + carry;
            digit = product % 10;
            factorial[j] = digit;
            carry = product / 10;
        } 
        while (carry) {
            digit = carry % 10;
            factorial[length] = digit;
            ++length;
            carry/=10;
        }
    }
    for (int k = length - 1; k >= 0; --k) {
         std::cout << factorial[k];
    }
}