Problem

#include <iostream>

const int N = 1000010;

using namespace std;

int n, q;

int a[N];

struct node
{
	int sum;
	int l, r;
	int lz;
}tree[N * 4];



void build (int k, int l, int r)

{
	tree[k].l = l;
	tree[k].r = r;
	tree[k].lz = -1;
	if (l == r)
	{
		tree[k].sum = a[l];
		return ;	
	} 
	int mid = (l + r) >> 1;
	build (k << 1, l, mid) , build (k << 1 | 1, mid + 1, r);
	tree[k].sum = tree[k << 1].sum + tree[k << 1 | 1].sum;
}

void lazy (int k, int v)

{
	tree[k].sum = v;
	tree[k].lz = v;	
}

void pushdown (int k)

{
	lazy (k << 1, tree[k].lz);
	lazy (k << 1 | 1, tree[k].lz);
	tree[k].lz = -1;
}

void modify (int k, int x, int y, int v)
{
	int l = tree[k].l , r = tree[k].r;
	if (l >= x && r <= y) return lazy (k, v); 
	if (tree[k].lz != -1) pushdown (k);
	int mid = (l + r) >> 1;
	if (x <= mid) modify (k << 1, x, y, v);
	if (y > mid) modify (k << 1 | 1, x, y, v);
	tree[k].sum = tree[k << 1].sum + tree[k << 1 | 1].sum;
}

int query (int x, int y, int k)

{
	int l = tree[k].l , r = tree[k].r;
	if (l >= x && r <= y) return tree[k].sum;
	if (tree[k].lz != -1) pushdown (k);
	int mid = (l + r) >> 1;
	int ans = 0;
	if (x <= mid) ans += query (x, y, k << 1);
	if (y > mid) ans += query (x, y, k << 1 | 1);
	return ans; 
}

int main()

{
	cin >> n >> q;
	for (int i = 1; i <= n; i ++) cin >> a[i];
	build (1, 1, n);
	while (q --)
	{
		int opt , l, r;
		cin >> opt >> l >> r;
		if (opt == 1)
		{
			int x;
			cin >> x;
			modify (1, l, r, x);
		}
		else
		{
			cout << query (l, r, 1) << endl;
		}
	}
}