Explanation

Let's consider $f$ when we've added two equations to it, $\{a, b\}, \{c, d\}$.

1. $c(ax + b) + d$
2. $acx + bc + d$

From this, we can make two observations.

1. In the expanded equation, $x$ is just multiplied by all of its coefficients.
2. Any constant is multiplied by all future coefficients.

We can calculate all of this on the fly as we process "add" and "compute" queries, but how do we deal with "removal" queries under a modulus?

Implementation

Time Complexity: $\mathcal{O}(\log n)$

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#include <bits/stdc++.h>
using namespace std;

using ll = long long;
const ll MOD = 998244353;

// source: https://usaco.guide/gold/modular#solution---exponentiation
ll bin_exp(ll x, ll n) {
	assert(n >= 0);