#include <iostream>

struct Bigint
{
    int len;
    int a[150005];

    Bigint(int x)
    {
        for (len = 1; x != 0; len++)
        {
            a[len] = x % 10;
            x /= 10;
        }
        len--;
    }

    int &operator[](int i) { return a[i]; }

    void flatten(int l)
    {
        len = l;
        for (int i = 1; i <= len; i++)
        {
            a[i + 1] += a[i] / 10;
            a[i] %= 10;
        }
        while (a[len] == 0 && len > 1)
            len--;
    }

    friend std::ostream &operator<<(std::ostream &output, const Bigint &x)
    {
        for (int i = x.len; i >= 1; i--)
            std::cout << x.a[i];
        return output;
    }
 
    friend std::istream &operator>>(std::istream &input, Bigint &x)
    {
        std::string str;
        std::cin >> str;
        x.len = 0;
        for (int i = 0; i < str.length(); i++)
            x.a[++x.len] = str[str.length() - i - 1] - '0';
        return input;
    }

    void operator=(const Bigint &y)
    {
        len = y.len;
        for (int i = 1; i <= len; i++)
            a[i] = y.a[i];
    }

    friend Bigint operator+(Bigint a, Bigint b)
    {
        Bigint res(0);
        for (int i = 1; i <= std::max(a.len, b.len); i++)
            res[i] = a[i] + b[i];
        res.flatten(std::max(a.len, b.len) + 1);
        return res;
    }

    friend bool operator<=(Bigint a, Bigint b)
    {
        if (a.len < b.len)
            return true;
        for (int i = a.len; i >= 1; i--)
            if (a.a[i] < b.a[i])
                return true;
        return (a.a[1] <= b.a[1]);
    }
};

Bigint n(0), a(1), b(1), c(1);

int main()
{
//    freopen("data.in", "r", stdin);
//    freopen("lzy.out", "w", stdout);

//    std::ios::sync_with_stdio(false);
//    std::cin.tie(nullptr);
//    std::cout.tie(nullptr);

    std::cin >> n;

    c = a + b;
    while (c <= n)
    {
        a = b;
        b = c;
        c = a + b;
    }

    std::cout << a << " " << b << " " << c << " " << n << "\n";

    return 0;
}

问号两行任意注释一个就能输入，留下来就输入都输不了。请问这是什么鬼？