#include "bits/stdc++.h"
using namespace std;
const int MAXN = 1e5 + 5;
int n , m , opt , x , y;
double a[MAXN] , t1[MAXN << 2] , t2[MAXN << 2] , tag1[MAXN << 2] , tag2[MAXN << 2] , k;

int ls(int p) {return p << 1;}

int rs(int p) {return (p << 1) + 1;}

void push_up(int p)
{
    t1[p] = t1[ls(p)] + t1[rs(p)];
    t2[p] = t2[ls(p)] + t2[rs(p)];
    return;
}

void build(int p , int l , int r)
{
    if (l == r) {t1[p] = a[l]; t2[p] = a[l] * a[l]; return;}
    int mid = (l + r) >> 1;
    build(ls(p) , l , mid);
    build(rs(p) , mid + 1 , r);
    push_up(p);
    return;
}

void add_tag1(int p , int l , int r , double d)
{
    tag1[p] += d;
    t1[p] += (r - l + 1) * d;
    return;
}

void push_down1(int p , int l , int r)
{
    int mid = (l + r) >> 1;
    add_tag1(ls(p) , l , mid , tag1[p]);
    add_tag1(rs(p) , mid + 1 , r , tag1[p]);
    tag1[p] = 0;
    return;
}

double query1(int x , int y , int p , int l , int r)
{
    if (x <= l && r <= y) return t1[p];
    push_down1(p , l , r);
    int mid = (l + r) >> 1;
    double ans = 0;
    if (x <= mid) ans += query1(x , y , ls(p) , l , mid);
    if (y > mid) ans += query1(x , y , rs(p) , mid + 1 , r);
    return ans; 
}

void add_tag2(int p , int l , int r , double d)
{
    tag2[p] += d;
    t2[p] += 2 * d * query1(l , r , 1 , 1 , n) + (r - l + 1) * d * d;
    return;
}

void push_down2(int p , int l , int r)
{
    int mid = (l + r) >> 1;
    add_tag2(ls(p) , l , mid , tag2[p]);
    add_tag2(rs(p) , mid + 1 , r , tag2[p]);
    tag2[p] = 0;
    return;
}

void update2(int x , int y , int p , int l , int r , double d)
{
    if (x <= l && r <= y)
    {
        add_tag2(p , l , r , d);
        return;
    }
    push_down2(p , l , r);
    int mid = (l + r) >> 1;
    if (x <= mid) update2(x , y , ls(p) , l , mid , d);
    if (y > mid) update2(x , y , rs(p) , mid + 1 , r , d);
    push_up(p);
    return;
}

void update1(int x , int y , int p , int l , int r , double d)
{
    if (x <= l && r <= y)
    {
        add_tag1(p , l , r , d);
        return;
    }
    push_down1(p , l , r);
    int mid = (l + r) >> 1;
    if (x <= mid) update1(x , y , ls(p) , l , mid , d);
    if (y > mid) update1(x , y , rs(p) , mid + 1 , r , d);
    push_up(p);
    return;
}

double query2(int x , int y , int p , int l , int r)
{
    if (x <= l && r <= y) return t2[p];
    push_down2(p , l , r);
    int mid = (l + r) >> 1;
    double ans = 0;
    if (x <= mid) ans += query2(x , y , ls(p) , l , mid);
    if (y > mid) ans += query2(x , y , rs(p) , mid + 1 , r);
    return ans; 
}

int main()
{
    cin >> n >> m;
    for (int i = 1 ; i <= n ; i++) cin >> a[i];
    build(1 , 1 , n);
    while (m--)
    {
        cin >> opt >> x >> y;
        if (opt == 1)
        {
            cin >> k;
            update2(x , y , 1 , 1 , n , k);
            update1(x , y , 1 , 1,  n , k);
        }
        else if (opt == 2)
        {
            cout << fixed << setprecision(4) << query1(x , y , 1 , 1 , n) / (y - x + 1) << '\n';
        }
        else
        {
            cout << fixed << setprecision(4) << query2(x , y , 1 , 1 , n) / (y - x + 1) - (query1(x , y , 1 , 1 , n) / (y - x + 1)) * (query1(x , y , 1 , 1 , n) / (y - x + 1)) << '\n';
        }
    }
    return 0;
}