Problem:
RSQ and RUQ

Write a program which manipulates a sequence $A$ = {$a_0, a_1, ..., a_{n-1}$} with the following operations:

$update(s, t, x)$: change $a_s, a_{s+1}, ..., a_t$ to $x$.

$getSum(s, t)$: print the sum of $a_s, a_{s+1}, ..., a_t$.

Note that the initial values of $a_i ( i = 0, 1, ..., n-1 )$ are 0.

Input

$n$ $q$
$query_1$
$query_2$
:
$query_q$

In the first line, $n$ (the number of elements in $A$) and $q$ (the number of queries) are given. Then, $i$-th query $query_i$ is given in the following format:

0 $s$ $t$ $x$

or

1 $s$ $t$

The first digit represents the type of the query. '0' denotes $update(s, t, x)$
and '1' denotes $find(s, t)$.

Output

For each $getSum$ query, print the sum in a line.

Constraints

$1 ≤ n ≤ 100000$

$1 ≤ q ≤ 100000$

$0 ≤ s ≤ t < n$

$-1000 ≤ x ≤ 1000$

Sample Input 1

6 7
0 1 3 1
0 2 4 -2
1 0 5
1 0 1
0 3 5 3
1 3 4
1 0 5

Sample Output 1

-5
1
6
8

Solution in C++14 (judge verdict: Accepted)

// clang-format off
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define main signed main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979;
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
bool odd(const int &n) { return n & 1; }
bool even(const int &n) { return ~n & 1; }
template<typename T = int> T in() { T x; cin >> x; return x; }
template<typename T = int> T in(T &&x) { T z(forward<T>(x)); cin >> z; return z; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &x : v) is >> x; return is; }
template<typename A, typename B> istream &operator>>(istream &is, pair<A, B> &p) { return is >> p.first >> p.second; }
template<typename T> ostream &operator<<(ostream &os, const vector<vector<T>> &v) { int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "" : "\n"); return os; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "" : " "); return os; }
template<typename A, typename B> ostream &operator<<(ostream &os, const pair<A, B> &p) { return os << p.first << ' ' << p.second; }
template<typename Head, typename Value> auto vectors(const Head &head, const Value &v) { return vector<Value>(head, v); }
template<typename Head, typename... Tail> auto vectors(Head x, Tail... tail) { auto inner = vectors(tail...); return vector<decltype(inner)>(x, inner); }
// clang-format on

template<typename LSTTrait> class LazySegTree {
  using FoldMonoid = typename LSTTrait::FoldMonoid;
  using ActionMonoid = typename LSTTrait::ActionMonoid;
  using T = typename FoldMonoid::value_type;
  using Q = typename ActionMonoid::value_type;

  LSTTrait lstTrait; // apply :: (T, Q) -> T, pow :: (Q, int) -> Q
  FoldMonoid foldM;
  ActionMonoid actionM;
  int size = 1;
  vector<T> tree; // 1-indexed
  vector<Q> lazy; // 1-indexed

  void push(int i) {
    stack<pair<int, int>> s;
    for (int d = 1; i /= 2; d *= 2) s.emplace(i, d);
    for (int x, d; s.size(); s.pop()) {
      tie(x, d) = s.top();
      update(x * 2, lazy[x], d);
      update(x * 2 + 1, lazy[x], d);
      lazy[x] = actionM.id();
    }
  }

  void update(const int &i, const Q &x, const int &d) {
    tree[i] = lstTrait.apply(tree[i], lstTrait.pow(x, d));
    if (i < size) lazy[i] = actionM(lazy[i], x);
  }

  void build(int i) {
    for (int d = 2; i /= 2; d *= 2) tree[i] = lstTrait.apply(foldM(tree[i * 2], tree[i * 2 + 1]), lstTrait.pow(lazy[i], d));
  }

public:
  LazySegTree(const int &n = 0) {
    while (size < n) size *= 2;
    tree.assign(size * 2, foldM.id());
    lazy.assign(size, actionM.id());
  }

  LazySegTree(const int &n, const T &x) {
    while (size < n) size *= 2;
    tree.assign(size * 2, x);
    lazy.assign(size, actionM.id());
    for (int i = size - 1; i >= 1; i--) tree[i] = foldM(tree[i * 2], tree[i * 2 + 1]);
  }

  template<typename InputIterator> LazySegTree(InputIterator first, InputIterator last) {
    int n = distance(first, last);
    while (size < n) size *= 2;
    tree.resize(size * 2, foldM.id());
    lazy.assign(size, actionM.id());
    copy(first, last, tree.begin() + size);
    for (int i = size - 1; i >= 1; i--) tree[i] = foldM(tree[i * 2], tree[i * 2 + 1]);
  }

  void act(int l, int r, const Q &x) { // [l, r) += x
    int l0 = l += size, r0 = r += size;
    push(l0), push(r0 - 1);
    for (int d = 1; l < r; l /= 2, r /= 2, d *= 2) {
      if (l & 1) update(l++, x, d);
      if (r & 1) update(--r, x, d);
    }
    build(l0);
    build(r0 - 1);
  }

  T fold(int l, int r) { // [l, r)
    T accl = foldM.id(), accr = foldM.id();
    for (push(l += size), push((r += size) - 1); l < r; l /= 2, r /= 2) {
      if (l & 1) accl = foldM(accl, tree[l++]);
      if (r & 1) accr = foldM(tree[--r], accr);
    }
    return foldM(accl, accr);
  }
};

template<typename T> struct sumMonoid {
  using value_type = T;
  value_type id() { return 0; }
  value_type operator()(const value_type &a, const value_type &b) { return a + b; }
};

template<typename T> struct updateMonoid {
  using value_type = pair<bool, T>;
  value_type id() { return {false, T()}; }
  value_type operator()(const value_type &a, const value_type &b) { return b.first ? b : a; }
};

template<typename T> struct RSQ_RUQ_Trait {
  using FoldMonoid = sumMonoid<T>;
  using ActionMonoid = updateMonoid<T>;
  typename FoldMonoid::value_type apply(typename FoldMonoid::value_type t, typename ActionMonoid::value_type q) { return q.first ? q.second : t; }
  typename ActionMonoid::value_type pow(typename ActionMonoid::value_type q, const int &d) { return {q.first, q.second * d}; }
};

main {
  int n, q;
  cin >> n >> q;
  LazySegTree<RSQ_RUQ_Trait<int>> lst(n, 0);
  while (q--) {
    if (in()) {
      int s, t;
      cin >> s >> t;
      cout << lst.fold(s, t + 1) << endl;
    } else {
      int s, t, x;
      cin >> s >> t >> x;
      lst.act(s, t + 1, {true, x});
    }
  }
}