Segtree update query build

/*
I am Hunting High and Low
Diving from the sky above
Looking for, more and more, once again
I'm Hunting High and Low
Sometimes I may win, sometimes I'll lose
It's just a game that I play

After the storm there's a calm
Through the clouds shines a ray of the sun
I'm carried from all my harm
There is no one I can't outrun

Now I'm leaving my worries behind
Feel the freedom of body and mind
I'm starting my journey, I'm drifting away with the wind, I go___________________:-
*/
#include<bits/stdc++.h>
using namespace std;

const int N = 1e5 + 50;

#define f(i,a,n) for(int i = a; i < n; i++)
#define L       cout << '\n';
#define pb(x)   push_back(x)
#define C(x)    cout << x << ' '
#define A(v)    v.begin(), v.end()
#define int     long long int
#define ff      first
#define ss      second

int tree[N << 2 + 5], arr[N];
void build(int l, int r, int node){

    if(l == r){
        tree[node] = arr[l];
        return;
    }

    int mid = (l + r) / 2;

    build(l, mid, node * 2);
    build(mid + 1, r, (node * 2 )+ 1);

    tree[node] = tree[node * 2] + tree[node * 2 + 1];
}
int query(int l, int r, int ql, int qr, int node ){
    if(r < ql || l > qr)return 0LL;

    if(ql <= l and r <= qr)
        return tree[node];

    int mid = (l + r) / 2;

    return query(l, mid, ql, qr, node * 2 + 1) + query(mid + 1, r, ql, qr, node * 2 + 1);
}
void update(int l, int r, int val, int pos, int node){

    if(l == r and l == pos){
        tree[node] = val;
        return;
    }

    if(pos < l || pos > r)return;

    int mid = (l + (r - l) / 2);

    update(l, mid, val, pos, 2 * node);
    update(mid + 1, r, val, pos, 2 * node + 1);
        tree[node] = tree[node * 2] + tree[node * 2 + 1];

}
signed main(){
       ios_base::sync_with_stdio(0);
       cin.tie(NULL);cout.tie(NULL);

        int n, i, l, r, q;
        cin >> n;

        for(i = 1; i <= n; i++){
            cin >> arr[i];
        }

        build(1, n, 1);

        cin >> q;

        while(q--){
            cin >> l >> r;
            update(1, n, l, r, 1);
        }
        C(query(1, n, 1, 3, 1));L;

  return 0;
}