Problem:
Score : 700 points

Problem Statement

You are given two sequences a and b, both of length 2N. The i-th elements in a and b are a_i and b_i, respectively.
Using these sequences, Snuke is doing the job of calculating the beauty of pairs of balanced sequences of parentheses (defined below) of length 2N.
The beauty of a pair (s,t) is calculated as follows:

Let X=0.

For each i between 1 and 2N (inclusive), increment X by a_i if s_i = t_i, and increment X by b_i otherwise.

The beauty of (s,t) is the final value of X.

You will be given Q queries. Process them in order.
In the i-th query, update the value of a_{p_i} to x_i, and the value of b_{p_i} to y_i. Then, find the maximum possible beauty of a pair of balanced sequences of parentheses.

In this problem, only the sequences below are defined to be balanced sequences of parentheses.

An empty string

The concatenation of (, s, ) in this order, where s is a balanced sequence of parentheses

The concatenation of s, t in this order, where s and t are balanced sequences of parentheses

Constraints

1 \leq N,Q \leq 10^{5}

-10^{9} \leq a_i,b_i,x_i,y_i \leq 10^{9}

1 \leq p_i \leq 2N

All input values are integers.

Partial Scores

In the test set worth 200 points, N \leq 5 and Q \leq 10.

In the test set worth 300 points, Q = 1.

Input

Input is given from Standard Input in the following format:

N Q
a_1 a_2 ... a_{2N}
b_1 b_2 ... b_{2N}
p_1 x_1 y_1
:
p_Q x_Q y_Q

Output

Print Q lines. The i-th line should contain the response to the i-th query.

Sample Input 1

2 2
1 1 7 3
4 2 3 3
2 4 6
3 2 5

Sample Output 1

15
15

The first query updates a and b to a=(1,4,7,3),b=(4,6,3,3). The maximum possible beauty is 15 for (s,t) =(()(),()()).

The second query updates a and b to a=(1,4,2,3),b=(4,6,5,3). The maximum possible beauty is 15 for (s,t) =(()(),(())).

Sample Input 2

7 7
34 -20 -27 42 44 29 9 11 20 44 27 19 -31 -29
46 -50 -11 20 28 46 12 13 33 -22 -48 -27 35 -17
7 27 34
12 -2 22
4 -50 -12
3 -32 15
8 -7 23
3 -30 11
4 -2 23

Sample Output 2

311
312
260
286
296
292
327

Solution in Rust (1.15.1) (judge verdict: Accepted)

//---------- begin SegmentTree Point update Range query ----------
mod segment_tree {
    pub struct PURQ<T: Clone, F: Fn(T, T) -> T> {
        n: usize,
        a: Vec<T>,
        id: T,
        op: F,
    }
    #[allow(dead_code)]
    impl<T: Clone, F: Fn(T, T) -> T> PURQ<T, F> {
        pub fn new(n: usize, id: T, op: F) -> PURQ<T, F> {
            let mut k = 1;
            while k < n {
                k *= 2;
            }
            PURQ {
                n: k,
                a: vec![id.clone(); 2 * k],
                id: id,
                op: op,
            }
        }
        pub fn update(&mut self, x: usize, v: T) {
            let mut k = self.n + x;
            let a = &mut self.a;
            a[k] = v;
            k >>= 1;
            while k > 0 {
                a[k] = (self.op)(a[2 * k].clone(), a[2 * k + 1].clone());
                k >>= 1;
            }
        }
        pub fn update_tmp(&mut self, x: usize, v: T) {
            self.a[x + self.n] = v;
        }
        pub fn update_all(&mut self) {
            for k in (1..(self.n)).rev() {
                self.a[k] = (self.op)(self.a[2 * k].clone(), self.a[2 * k + 1].clone());
            }
        }
        pub fn find(&self, mut l: usize, mut r: usize) -> T {
            let mut p = self.id.clone();
            let mut q = self.id.clone();
            l += self.n;
            r += self.n;
            while l < r {
                if (l & 1) == 1 {
                    p = (self.op)(p, self.a[l].clone());
                    l += 1;
                }
                if (r & 1) == 1 {
                    r -= 1;
                    q = (self.op)(self.a[r].clone(), q);
                }
                l >>= 1;
                r >>= 1;
            }
            (self.op)(p, q)
        }
    }
}
//---------- end SegmentTree Point update Range query ----------
//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

//

use std::io::Write;

fn run() {
    let out = std::io::stdout();
    let mut out = std::io::BufWriter::new(out.lock());
    input! {
        n: usize,
        q: usize,
        a: [i64; 2 * n],
        b: [i64; 2 * n],
        p: [(usize1, i64, i64); q],
    }
    type T = (i64, i64);
    let f = |a: T, b: T| (std::cmp::max(a.0 + b.0, a.1 + b.1), std::cmp::max(a.0 + b.1, a.1 + b.0));
    let mut s = segment_tree::PURQ::new(2 * n, (0, std::i64::MIN / 4), f);
    for i in 1..(2 * n - 1) {
        s.update_tmp(i, (a[i], b[i]));
    }
    s.update_all();
    let mut a = a;
    let mut b = b;
    for (p, x, y) in p {
        if 0 < p && p < 2 * n - 1 {
            s.update(p, (x, y));
        }
        a[p] = x;
        b[p] = y;
        let mut ans = a[0] + a[2 * n - 1];
        if n > 1 {
            ans += s.find(1, 2 * n - 1).0;
        }
        writeln!(out, "{}", ans).ok();
    }
}

fn main() {
    run();
}