#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e6;
double a[N],b[N];
double tr1[N],tr2[N];
double lazy[N];

inline void push_up(int id)
{
	tr1[id]=tr1[id<<1]+tr1[id<<1|1];
	tr2[id]=tr2[id<<1]+tr2[id<<1|1];
}
inline void push_down(int id,int l,int r) 
{
	int mid=(l+r)>>1;
	lazy[id<<1]+=lazy[id];
	lazy[id<<1|1]+=lazy[id];
	tr2[id<<1]+=(lazy[id]*lazy[id])*(mid-l+1)+(2*lazy[id])*tr1[id<<1];
	tr2[id<<1|1]+=(lazy[id]*lazy[id])*(r-mid)+(2*lazy[id])*tr1[id<<1|1];

	tr1[id<<1]+=lazy[id]*(mid-l+1);
	tr1[id<<1|1]+=lazy[id]*(r-mid);
	lazy[id]=0;
}
inline void build(int id,int l,int r)
{
	if(l==r)
	{
		tr1[id]=a[l];
		tr2[id]=a[l]*a[l];
		
		return;
	}
	int mid = (l+r)>>1;
	build(id<<1,l,mid);
	build(id<<1|1,mid+1,r);
	push_up(id);
}

inline void update(int id,int l,int r,int x,int y,double v)
{
	if(x<=l&&r<=y)
	{
		lazy[id]+=v;
		tr2[id]+=(2*v)*tr1[id]+(v*v)*(r-l+1);
		tr1[id]+=v*(r-l+1);
		return;
	}
	int mid= (l+r) >>1;
	push_down(id,l,r);
	if(x<=mid)
	{
		update(id<<1,l,mid,x,y,v);
	}
	else
	{
		update(id<<1|1,mid+1,r,x,y,v);
	}
	push_up(id);
}

inline double find(int id,int l,int r,int x,int y,int n)
{
	if(x<=l&&r<=y) 
	{
		if(n==1)
		{
			return tr1[id];
		}
		if(n==2)
		{
			return tr2[id];
		}
	}
	int mid =(l+r)>>1;
	double all=0;
	push_down(id,l,r);
	if(x<=mid)
	{
		all+=find(id<<1,l,mid,x,y,n);
	}
	if(y>mid)
	{
		all+=find(id<<1|1,mid+1,r,x,y,n);
	}
	return all;
}

signed main()
{
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	build(1,1,n);
	for(int i=1;i<=m;i++)
	{
		int x;
		cin>>x;
		if(x==1)
		{
			int y,z;
			double k;
			cin>>y>>z>>k;
			update(1,1,n,y,z,k);
		}
		if(x==2)
		{
			int y,z;
			cin>>y>>z;
			double en = find(1,1,n,y,z,1)/((z-y+1)*1.0);
			printf("%.4lf\n",en);
		}
		if(x==3)
		{
			int y,z;
			cin>>y>>z;
			//cout<<find(1,1,n,y,z,2)<<" "<<find(1,1,n,y,z,1)<<endl;
			double l = find(1,1,n,y,z,2)/((z-y+1)*1.0)-(find(1,1,n,y,z,1)/((z-y+1)*1.0))*(find(1,1,n,y,z,1)/((z-y+1)*1.0));
			printf("%.4lf\n",l);
		}
	}
}