rt记录，样例都没过QAQ：

#include<bits/stdc++.h>
using namespace std;

const int N=1e5+5;
int n,m;
double t1[N<<2],t2[N<<2],tag[N<<2];

inline int lc(int x){
	return x<<1;
}
inline int rc(int x){
	return x<<1|1;
}
inline double pw(double x){
	return x*x;
}

void pushup(int x){
	t1[x]=t1[lc(x)]+t1[rc(x)];
	t2[x]=t2[lc(x)]+t2[rc(x)];
}

void buildtree(int x,int l,int r){
	if(l==r){
		scanf("%lf",&t1[x]);
		t2[x]=pw(t1[x]);
		return ;
	}
	int mid=(l+r)/2;
	buildtree(lc(x),l,mid);
	buildtree(rc(x),mid+1,r);
	pushup(x);
}

void pushdown(int x,int l,int r){
	int len=r-l+1;
	if(tag[x]){
		t1[lc(x)]+=(len-len/2)*tag[x];
		t1[rc(x)]+=(len/2)*tag[x];
		t2[lc(x)]+=2*tag[x]*t1[lc(x)]+(len-len/2)*tag[x]*tag[x];
        t2[rc(x)]+=2*tag[x]*t1[rc(x)]+(len/2)*tag[x]*tag[x];
        tag[x]=0;
	}
}

void update(int x,int l,int r,int l1,int r1,double d){
	if(l1<=l&&r<=r1){
		t1[x]+=d*(r-l+1);
		t2[x]+=2*d*t1[x]+d*d*(r-l+1);
		tag[x]+=d;
		return ;
	}
	pushdown(x,l,r);
	int mid=(l+r)/2;
	if(l1<=mid)update(lc(x),l,mid,l1,r1,d);
	if(mid<r1)update(rc(x),mid+1,r,l1,r1,d);
	pushup(x);
}

double query1(int x,int l,int r,int l1,int r1){
	if(l1<=l&&r<=r1) return t1[x];
	pushdown(x,l,r);
	int mid=(l+r)/2;
	double res=0;
	if(l1<=mid)res+=query1(lc(x),l,mid,l1,r1);
	if(mid<r1)res+=query1(rc(x),mid+1,r,l1,r1);
	return res;
}

double query2(int x,int l,int r,int l1,int r1){
	if(l1<=l&&r<=r1) return t2[x];
	pushdown(x,l,r);
	int mid=(l+r)/2;
	double res=0;
	if(l1<=mid)res+=query2(lc(x),l,mid,l1,r1);
	if(mid<r1)res+=query2(rc(x),mid+1,r,l1,r1);
	return res;
}

signed main(){
	int op,x,y;
	double k;
	scanf("%d%d",&n,&m);
	buildtree(1,1,n);
	while(m--){
		scanf("%d",&op);
		if(op==1){
			scanf("%d%d%lf",&x,&y,&k);
			update(1,1,n,x,y,k);
		}else if(op==2){
			scanf("%d%d",&x,&y);
			printf("%.4lf\n",query1(1,1,n,x,y)/(y-x+1));
		}else{
			scanf("%d%d",&x,&y);
			double num1=query2(1,1,n,x,y)/(y-x+1);
			double num2=query1(1,1,n,x,y)/(y-x+1);
			printf("%.4lf\n",num1-pw(num2)); 
		}
	} 
    return 0;
}