#include <bits/stdc++.h>

using namespace std;

#define int long long

const int N = 1e5 + 10;

double a[N];

struct Node
{
    double sum, sum2;
    int sz; 
    double tag;
} tr[N << 2];

#define lson (rt << 1)
#define rson (rt << 1 | 1)
#define mid (l + r) / 2

void push_up(Node &a, Node b, Node c)
{ 
    a.sum = b.sum + c.sum;
    a.sum2 = b.sum2 + c.sum2;
}

void build(int rt, int l, int r)
{
    tr[rt] = {0, 0, r - l + 1, 0};
    if (l == r) return tr[rt] = {a[l], a[l] * a[l], 1, 0}, void();
    build(lson, l, mid);
    build(rson, mid + 1, r);
    push_up(tr[rt], tr[lson], tr[rson]);
}

void push_down(int rt)
{
    double &u = tr[rt].tag;
    if (u)
    {
        // (a^2) -> (a + x) ^ 2 -> a^2 + 2ax + x^2
        tr[lson].sum2 += tr[lson].sum * 2 * u + tr[lson].sz * u * u;
        tr[rson].sum2 += tr[rson].sum * 2 * u + tr[rson].sz * u * u;
        tr[lson].sum += tr[lson].sz * u;
        tr[rson].sum += tr[rson].sz * u;
        tr[lson].tag += u;
        tr[rson].tag += u;
        u = 0;
    }
}

void update(int rt, int l, int r, int sp, int ep, int v)
{
    if (sp <= l && r <= ep)
    {
        tr[rt].sum2 += tr[rt].sum * 2 * v + tr[rt].sz * v * v;
        tr[rt].sum += tr[rt].sz * v;
        tr[rt].tag += v;
        return;
    }
    push_down(rt);
    if (sp <= mid) update(lson, l, mid, sp, ep, v);
    if (ep > mid) update(rson, mid + 1, r, sp, ep, v);
    push_up(tr[rt], tr[lson], tr[rson]);
}

Node query(int rt, int l, int r, int sp, int ep)
{
    if (sp <= l && r <= ep) return tr[rt];
    Node res = {0, 0, 0};
    push_down(rt);
    if (sp <= mid) res = query(lson, l, mid, sp, ep);
    if (ep > mid) push_up(res, res, query(rson, mid + 1, r, sp, ep));
    return res;
}

int n, m;

signed main()
{
    scanf("%lld%lld", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%lf", &a[i]);
    build(1, 1, n);
    while (m--)
    {
        int op, l, r;
        scanf("%lld%lld%lld", &op, &l, &r);
        if (op == 1)
        {
            double k;
            scanf("%lf", &k);
            update(1, 1, n, l, r, k);
        }
        else if (op == 2)
        {
            double d = query(1, 1, n, l, r).sum;
            double x = (1.0 * d) / (r - l + 1);
            printf("%.4lf\n", x);
        }
        else
        {
            // a^2 - 2ab + b^2
            Node t = query(1, 1, n, l, r);
            double a = t.sum2 / (1.0 * (r - l + 1)), b = t.sum / (1.0 * (r - l + 1));
            double res = a - b * b;
            printf("%.4lf\n", res);
        }
    }
    return 0;
}