Unexpected TLE with Segment tree

#include <bits/stdc++.h>
using namespace std;
    
#define int long long
    
const int MAXN = 1e5 + 1;

// Globals
    
int n;
int a[MAXN];
int b[MAXN];
    
    
// Segment Tree
    
typedef pair <int, int> pii;

inline pii value(int i) {
    if(a[i] >= b[i]) // extra water
        return {a[i] - b[i], 0};
    else //too little water
        return {0, b[i] - a[i]};
}
    
inline pii combine(pii x, pii y) {
    auto [base_x, cutoff_x] = x;
    auto [base_y, cutoff_y] = y;
    
    int base_z, cutoff_z;
    
    base_z = base_y;
    if(base_x > cutoff_y)
        base_z += base_x - cutoff_y;
    
    cutoff_z = cutoff_x;
    if(base_x < cutoff_y)
        cutoff_z += cutoff_y - base_x;
    
    return {base_z, cutoff_z};
}
    
pii tree[4*MAXN];
    
inline void update_helper(int p, int tl, int tr, int i) {
    if(tl == p && tr == p) 
        tree[i] = value(p);
    else {
        int tm = (tl + tr) / 2;
        if(p <= tm)
            update_helper(p, tl, tm, 2*i);
        else
            update_helper(p, tm+1, tr, 2*i+1);
        tree[i] = combine(tree[2*i], tree[2*i+1]);
    }
}
    
    
inline void update(int p) {
    update_helper(p, 0, n - 1, 1);
}
    
inline void build_helper(int size, int tl, int tr, int i) {
    if(tl == tr) {
        if(tl < size)
            tree[i] = value(tl);
        else
            tree[i] = {0, 0};
    } else {
        int tm = (tl + tr) / 2;
        build_helper(size, tl, tm, 2*i);
        build_helper(size, tm + 1, tr, 2*i+1);
        tree[i] = combine(tree[2*i], tree[2*i+1]);
    }
}
    
inline void build(int size) {
    build_helper(size, 0, n - 1, 1);
}
    
    
    
void solve() {
    cin >> n;
    
    int q;
    cin >> q;
    
    for(int i = 0; i < n; i++)
        cin >> a[i];
    
    for(int i = 0; i < n; i++)
        cin >> b[i];
    
    for(int i = 0; i < n - 1; i++) {
        int x;
        cin >> x;
    }
    
    build(n);
    
    int total = 0;
    for(int i = 0; i < n; i++)
        total += a[i];
    
    while(q-- > 0) {
        int p, x, y, z;
        cin >> p >> x >> y >> z;
    
        p--;
    
        total += x - a[p];
        a[p] = x;
        b[p] = y;
        update(p);
    
        auto [base, cutoff] = tree[1];
        cout << total - base << "\n";
    }
}
        
int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);    
    
    int t = 1;
    
    while(t-- > 0) 
        solve();
}