segment tree 01

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

#define ll long long
const int sz=100005;

double ar[3*sz];
double tree[3*sz];

void ini(int node,int b, int e)
{
    if(b==e) {tree[node]=ar[b]; return ;}
    int left=node*2;
    int right = node*2 +1;
    int mid=(b+e)/2;
    ini(left,b,mid);
    ini(right,mid+1,e);
    tree[node]=tree[left]+tree[right];
}
double query(int node, int b, int e, int i, int j)
{
    if(i>e||j<b) return 0;
    if(b>=i&&e<=j) return tree[node];
    int left= node*2;
    int right = node*2 +1;
    int mid= (b+e)/2;
    double p1= query(left,b,mid,i,j);
    double p2= query(right,mid+1,e,i,j);
    return p1+p2;
}
void update(int node,int b,int e,int i,double newvalue)
{
    if(i>e||i<b) return;
    if(b>=i&&e<=i)
    {
        tree[node]= newvalue;
        return ;
    }
    int left=node*2;
    int right = node*2 +1;
    int mid= (b+e)/2;
    update(left,b,mid,i,newvalue);
    update(right,mid+1,e,i,newvalue);
    tree[node] = tree[left]+tree[right];
}
int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>ar[i];
    }
    ini(1,0,n-1);
    int q;
    cin>>q;
    while(q--){
        int a;
        cin>>a;
        if(a==1){
            int x;
            double y;
            cin>>x>>y;
            update(1,0,n-1,x-1,y);
        }
        else{
            int m,nn;
            cin>>m>>nn;
            double que=query(1,0,n-1,m-1,nn-1);
            double v=(que/(nn-m+1.0));
            cout<<fixed<<setprecision(6)<<v<<endl;
        }
    }
}