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struct SegTree {
using T = ll; using U = ll;
static constexpr T E = 0; // Neutral element for combine
static constexpr U UF = 0; // Unused value by updates
int n;
vector<T> tree; vector<U> lazy;
int h;
vector<ll> k; // size of segments (optional)
SegTree(const vector<T>& a) : n(ssize(a) + 1), tree(2 * n),
//SegTree(int size, T def = E) : n(size + 1), tree(2 * n, def),
lazy(n, UF), h(__lg(2 * n)), k(2 * n, 1) {
ranges::copy(a, tree.begin() + n);
for (int i = n - 1; i > 0; i--) {
k[i] = 2 * k[2 * i];
tree[i] = comb(tree[2 * i], tree[2 * i + 1]);
}}
T comb(T a, T b) { return a + b; } // Modify this + E
void apply(int i, U val) { // And this + UF
tree[i] = val * k[i];
if (i < n) lazy[i] = val; // Don't forget this
}
void push_down(int i) {
if (lazy[i] != UF) {
apply(2 * i, lazy[i]);
apply(2 * i + 1, lazy[i]);
lazy[i] = UF;
}}
void push(int i) {
for (int s = h; s > 0; s--) push_down(i >> s);
}
void build(int i) {
while (i /= 2) {
push_down(i);
tree[i] = comb(tree[2 * i], tree[2 * i + 1]);
}}
void update(int l, int r, U val) {
l += n, r += n;
int l0 = l, r0 = r;
push(l0), push(r0);
for (; l < r; l /= 2, r /= 2) {
if (l&1) apply(l++, val);
if (r&1) apply(--r, val);
}
build(l0), build(r0);
}
T query(int l, int r) {
l += n, r += n;
push(l), push(r);
T resL = E, resR = E;
for (; 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);
}
// Optional:
ll lower_bound(int l, int r, T x) {
l += n, r += n;
push(l), push(r - 1);
int a[64] = {}, lp = 0, rp = 64;
for (; l < r; l /= 2, r /= 2) {
if (l&1) a[lp++] = l++;
if (r&1) a[--rp] = --r;
}
for (int i : a) if (i != 0 && tree[i] >= x) { // Modify this
while (i < n) {
push_down(i);
if (tree[2 * i] >= x) i = 2 * i; // And this
else i = 2 * i + 1;
}
return i - n;
}
return -1;
}
};
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