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struct SegTree {
using T = ll;
int n;
vector<T> tree;
static constexpr T E = 0; // Neutral element for combine
SegTree(vector<T>& a) : n(sz(a)), tree(2 * n) {
//SegTree(int size, T val = E) : n(size), tree(2 * n, val) {
copy(all(a), tree.begin() + n);
for (int i = n - 1; i > 0; i--) { // remove for range update
tree[i] = comb(tree[2 * i], tree[2 * i + 1]);
}}
ll comb(T a, T b) {return a + b;} // modify this + neutral
void update(int i, T val) {
tree[i += n] = val; // apply update code
while (i /= 2) tree[i] = comb(tree[2 * i], tree[2 * i + 1]);
}
T query(int l, int r) {
T resL = E, resR = E;
for (l += n, r += n; l < r; l /= 2, r /= 2) {
if (l&1) resL = comb(resL, tree[l++]);
if (r&1) resR = comb(tree[--r], resR);
}
return comb(resL, resR);
}
// OR: range update + point query, needs commutative comb
void modify(int l, int r, T val) {
for (l += n, r += n; l < r; l /= 2, r /= 2) {
if (l&1) tree[l] = comb(tree[l], val), l++;
if (r&1) --r, tree[r] = comb(tree[r], val);
}}
T query(int i) {
T res = E;
for (i += n; i > 0; i /= 2) res = comb(res, tree[i]);
return res;
}
};
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