#include<iostream>
#include<cstdio>
#include<cmath>
#include<string>
#include<cstring>
#include<algorithm>
#include<cassert>
#include<stack>
#include<queue>
#include<vector>
#include<map>
#include<cstdlib>
using namespace std;
#define ll long long
#define ull unsigned long long
int read()
{
	int now=0,nev=1; 
	char c=getchar();
	while(c<'0' || c>'9') 
	{ 
		if(c=='-') 
			nev=-1; 
		c=getchar();
	}
	while(c>='0' && c<='9') 
	{ 
		now=(now<<1)+(now<<3)+(c&15); 
		c=getchar(); 
	}
	return now*nev;
}
const int MAXN=1e5+10;
int n,m;
double a[MAXN];
struct node
{
	int l,r;
	double sum,pfsum,add;
}tr[MAXN<<2];
void update(int k)
{
	tr[k].sum=tr[k<<1].sum+tr[k<<1|1].sum;
	tr[k].pfsum=tr[k<<1].pfsum+tr[k<<1|1].pfsum;
}
void build(int k,int l,int r)
{
	tr[k].l=l,tr[k].r=r;
	if(l==r)
	{
		tr[k].sum=a[l];
		tr[k].pfsum=a[l]*a[l];
		return ;
	}
	int m=l+r>>1;
	build(k<<1,l,m);
	build(k<<1|1,m+1,r);
	update(k);
}
void pushdown(int k)
{
	if(tr[k].add)
	{
		tr[k<<1].add+=tr[k].add;
		tr[k<<1|1].add+=tr[k].add;
		tr[k<<1].sum+=tr[k].add*(tr[k<<1].r-tr[k<<1].l+1);
		tr[k<<1|1].sum+=tr[k].add*(tr[k<<1|1].r-tr[k<<1|1].l+1);
		tr[k<<1].pfsum+=2*tr[k].add*tr[k<<1].sum+tr[k<<1].add*tr[k<<1].add*(tr[k<<1].r-tr[k<<1].l+1);
		tr[k<<1|1].pfsum+=2*tr[k].add*tr[k<<1|1].sum+tr[k<<1|1].add*tr[k<<1|1].add*(tr[k<<1|1].r-tr[k<<1|1].l+1);
		tr[k].add=0;
	}
}
void modefy(int k,int l,int r,double v)
{
	if(l<=tr[k].l && tr[k].r<=r)
	{
		tr[k].add+=v;
		tr[k].sum+=v*(tr[k].r-tr[k].l+1);
		tr[k].pfsum+=(2*tr[k].sum*v+v*v*(tr[k].r-tr[k].l+1));
		return ;
	}
	pushdown(k);
	int m=tr[k].l+tr[k].r>>1;
	if(l<=m)
		modefy(k<<1,l,r,v);
	if(r>m)
		modefy(k<<1|1,l,r,v);
	update(k); 
}
double query_sum(int k,int l,int r)
{
	if(l<=tr[k].l && tr[k].r<=r)
		return tr[k].sum;
	pushdown(k);
	int m=tr[k].l+tr[k].r>>1;
	double res=0;
	if(l<=m)
		res+=query_sum(k<<1,l,r);
	if(r>m)
		res+=query_sum(k<<1|1,l,r);
	return res;
}
double query_pfsum(int k,int l,int r)
{
	if(l<=tr[k].l && tr[k].r<=r)
		return tr[k].pfsum;
	pushdown(k);
	int m=l+r>>1;
	double res=0;
	if(l<=m)
		res+=query_pfsum(k<<1,l,r);
	if(r>m)
		res+=query_pfsum(k<<1|1,l,r);
	return res;
}
int main()
{
	memset(tr,0,sizeof(tr));
	n=read(),m=read();
	for(int i=1;i<=n;i++)
		scanf("%lf",&a[i]);
	build(1,1,n);
	for(int i=1;i<=m;i++)
	{
		int op;
		op=read();
		if(op==1)
		{
			double x,y,k;
			scanf("%lf%lf%lf",&x,&y,&k);
			modefy(1,x,y,k);
		}
		if(op==2)
		{
			double x,y;
			scanf("%lf%lf",&x,&y);
			printf("%.4lf\n",(double)((query_sum(1,x,y)*1.0/(y-x+1.0))));
		}
		if(op==3)
		{
			double x,y;
			scanf("%lf%lf",&x,&y);
			double sum=query_sum(1,x,y)*1.0/(y-x+1.0);
			printf("%.4lf\n",(double)(query_pfsum(1,x,y)*1.0/(y-x+1.0)-sum*sum*1.0));
		}
	}
	return 0;
}