#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=100010;
struct node{
    int l,r;
    double sum,squ,add;
}tr[N*4];
int n,m;
double w[N];
void pushup(int u){
    tr[u].sum=tr[u<<1].sum+tr[u<<1|1].sum;
    tr[u].squ=tr[u<<1].squ+tr[u<<1|1].squ;
}
void pushdown(int u){
    tr[u<<1].add+=tr[u].add;
    tr[u<<1|1].add+=tr[u].add;
    tr[u<<1].squ+=2*tr[u].add*tr[u<<1].sum+(tr[u<<1].l-tr[u<<1].r+1)*tr[u].add*tr[u].add;
    tr[u<<1|1].squ+=2*tr[u].add*tr[u<<1|1].sum+(tr[u<<1|1].l-tr[u<<1|1].r+1)*tr[u].add*tr[u].add;
    tr[u<<1].sum+=(tr[u<<1].r-tr[u<<1].l+1)*tr[u].add;
    tr[u<<1|1].sum+=(tr[u<<1|1].r-tr[u<<1|1].l+1)*tr[u].add;
    tr[u].add=0;
}
void build(int u,int l,int r){
    if(l==r)tr[u]={l,r,w[r],w[r]*w[r],0};
    else{
        tr[u]={l,r,0,0,0};
        int mid=l+r>>1;
        build(u<<1,l,mid),build(u<<1|1,mid+1,r);
        pushup(u);
    }
}
void modify(int u,int l,int r,double v){
    if(tr[u].l>=l&&tr[u].r<=r){
        tr[u].add+=v;
        tr[u].squ+=2*v*tr[u].sum+(tr[u].r-tr[u].l+1)*v*v;
        tr[u].sum+=(tr[u].r-tr[u].l+1)*v;
    }
    else{
        pushdown(u);
        int mid=tr[u].l+tr[u].r>>1;
        if(l<=mid)modify(u<<1,l,r,v);
        if(r>mid)modify(u<<1|1,l,r,v);
        pushup(u);
    }
}
double query(int u,int l,int r,int op){
    if(tr[u].l>=l&&tr[u].r<=r){
        if(op==2)return tr[u].sum;
        return tr[u].squ;
    }
    pushdown(u);
    int mid=tr[u].l+tr[u].r>>1;
    double ans=0;
    if(l<=mid)ans+=query(u<<1,l,r,op);
    if(r>mid)ans+=query(u<<1|1,l,r,op);
    return ans;
}
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)scanf("%lf",&w[i]);
    build(1,1,n);
    int op,x,y;
    while(m--){
        scanf("%d%d%d",&op,&x,&y);
        if(op==1){
            double k;
            scanf("%lf",&k);
            modify(1,x,y,k);
        }
        else if(op==2){
            double t=query(1,x,y,2);
            double ans=t/(y-x+1);
            printf("%.4lf\n",ans);
        }
        else {
            double t=query(1,x,y,3);
            double p=query(1,x,y,2);
            double ans=t/(y-x+1)-((p/(y-x+1))*(p/(y-x+1)));
            printf("%.4lf\n",ans);
        }
    }
    return 0;
}