Задача C informatics

#include <iostream>
#include <vector>

using namespace std;

const long long INF = 1e9;

void build(vector<long long>& a, vector<long long>& z, int l, int r, int now) {
	if (l > r) {
		return;
	}
	if (l == r) {
		z[now] = a[l];
		return;
	}
	int mid = (l + r) / 2;
	build(a, z, l, mid, now * 2);
	build(a, z, mid + 1, r, now * 2 + 1);
	if (z[now * 2] == z[now * 2 + 1] && z[now * 2] != -1 && z[now * 2 + 1] != -1) {
		z[now] = z[now * 2];
	}
	else {
		z[now] = -1;
	}
}

void update(vector<long long>& z, int l, int r, int a, int b, int now, int value) {
	if (l > r || a > r || b < l) {
		return;
	}
	if (l == r) {
		z[now] = value;
		return;
	}
	int mid = (l + r) / 2;
	update(z, l, mid, a, b, now * 2, value);
	update(z, mid + 1, r, a, b, now * 2 + 1, value);
	if (z[now * 2] == z[now * 2 + 1] && z[now * 2] != -1 && z[now * 2 + 1] != -1) {
		z[now] = z[now * 2];
	}
}

int query(vector<long long>& z, int l, int r, int ind, int now) {
	if (l > r || !(l <= ind && ind <= r)) {
		return -INF;
	}
	if (z[now] != -1) {
		return z[now];
	}
	else {
		int mid = (l + r) / 2;
		if (l <= ind && ind <= mid) {
			return query(z, l, mid, ind, now * 2);
		}
		else {
			return query(z, mid + 1, r, ind, now * 2 + 1);
		}
	}
}

int main()
{
	int n;
	cin >> n;
	vector<long long> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	vector<long long> z(n * 2, 0);
	build(a, z, 0, n - 1, 1);
	int m;
	cin >> m;
	for (int i = 0; i < m; ++i) {
		char c;
		cin >> c;
		if (c == 'g') {
			int ind;
			cin >> ind;
			ind--;
			cout << query(z, 0, n - 1, ind, 1) << " ";
		}
		else if (c == 'a') {
			int l, r, value;
			cin >> l >> r >> value;
			l--;
			r--;
			update(z, 0, n - 1, l, r, 1, value);
		}
	}
}