//方差
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using db = double;
#define rep(i, a, b) for(int i = (a); i <= (b); ++i)
#define pre(i, a, b) for(int i = (a); i >= (b); --i)
#define il inline
#define mem(a, b) memset(a, b, sizeof a)
#define debug(x) cerr << #x << '=' << x << ' '
#define FILE(x) freopen(x".in", "r", stdin), freopen(x".out", "w", stdout)
const int N = 1e5 + 10;
int n, m;
db a[N];
template<typename T, const int N>
class segment_tree {
  public:
	#define mid ((l + r) >> 1)
	#define ls (p << 1)
	#define rs (p << 1 | 1)
	struct node {
		T sum, ping;
		T add_tag;
		il node(): sum(0), ping(0), add_tag(0) {}
		il node operator + (const node &b) const {
			node res;
			res.sum = sum + b.sum;
			res.ping = ping + b.ping;
			res.add_tag = 0;
			return res;
		}
	} t[N << 2];
  private:
	il void Apply_add(int p, int l, int r, T k) {
		t[p].add_tag += k;
		t[p].ping += (2.0 * k * t[p].sum + (r - l + 1) * k * k);
		t[p].sum += (k * (r - l + 1));
	}
	il void Push_down(int p, int l, int r) {
		if(t[p].add_tag != 0)
		{
			Apply_add(ls, l, mid, t[p].add_tag);
			Apply_add(rs, mid + 1, r, t[p].add_tag);
			t[p].add_tag = 0;
		}
	}
  public:
	il void build_tree(int p, int l, int r) {
		if(l == r)
		{
			t[p].sum = a[l];
			t[p].ping = a[l] * a[l];
			t[p].add_tag = 0;
			return;
		}
		build_tree(ls, l, mid);
		build_tree(rs, mid + 1, r);
		t[p] = t[ls] + t[rs];
	}
	il void modify(int p, int l, int r, int x, int y, T k) {
		if(r < x || y < l) return;
		if(x <= l && r <= y)
		{
			Apply_add(p, l, r, k);
			return;
		}
		Push_down(p, l, r);
		if(x <= mid) modify(ls, l, mid, x, y, k);
		if(y > mid) modify(rs, mid + 1, r, x, y, k);
		t[p] = t[ls] + t[rs];
	}
	il node query(int p, int l, int r, int x, int y) {
		if(x <= l && r <= y)
			return t[p];
		Push_down(p, l, r);
		if(y <= mid) return query(ls, l, mid, x, y);
		if(x > mid) return query(rs, mid + 1, r, x, y);
		return query(ls, l, mid, x, y) + query(rs, mid + 1, r, x, y);
	}
};
segment_tree<db, N> T;
int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0), std::cout.tie(0);
	cin >> n >> m;
	rep(i, 1, n) cin >> a[i];
	T.build_tree(1, 1, n);
	while(m--)
	{
		int opt, x, y, k;
		cin >> opt >> x >> y;
		if(opt == 1)
		{
			cin >> k;
			T.modify(1, 1, n, x, y, k);
		}
		if(opt == 2)
		{
			cout << fixed << setprecision(4) << 1.0 * T.query(1, 1, n, x, y).sum / (y - x + 1) << '\n';
		}
		if(opt == 3)
		{
			segment_tree<db, N>::node tmp = T.query(1, 1, n, x, y);
			db sum = tmp.sum;
			db ping = tmp.ping;
			db average = sum / (y - x + 1);
			cout << fixed << setprecision(4) << 1.0 * ping / (y - x + 1) - 1.0 * average * average << '\n';
		}
	}
	return 0;
}

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