// ~/.vim/cpp_template.cpp
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#define REP(i,a,b) for (int i = a; i < b; i++)
// Type Aliases for 1D and 2D vectors with initialization
#define vll(n, val) vector<long long>(n, val) // 1D vector of long longs with size n, initialized to val
#define ll long long
#define vvi(n, m, val) vector<vector<int>>(n, vector<int>(m, val)) // 2D vector of ints (n x m), initialized to val
#define vvll(n, m, val) vector<vector<long long>>(n, vector<long long>(m, val)) // 2D vector of long longs (n x m), initialized to val
using namespace std;
template <typename T>
void pV(const std::vector<T>& vec, const std::string& label = "Vector") {
std::cout << label << ": [ ";
for (const auto& elem : vec) {
std::cout << elem << " ";
}
std::cout << "]" << std::endl;
}
using namespace std;
void dfs(int s, vector<bool> *visited, vector<int> (*adj)[]) {
if ((*visited)[s]) return;
(*visited)[s] = true;
// process node s
for (auto u: (*adj)[s]) {
dfs(u, visited, adj);
}
}
/*
vector<int> adj[N];
vector<bool> visited(N, false);
int u, v;
for(int i = 0; i < M;i++){
cin >> u >> v;
u--;
v--;
adj[u].push_back(v);
adj[v].push_back(u);
}
*/
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
// Your code starts here
int n, q;
cin >> n >> q;
vector<long long> vi(n, 0);
vector<int> vals(n, 0);
REP(i, 0, n){
cin >> vals[i];
if(i>0){
vi[i] += vi[i-1];
}
vi[i] += vals[i];
}
REP(i, 0, q){
int a, b;
cin >> a >> b;
a--;
b--;
double avg;
if(a==0){
avg = vi[b];
}else{
avg = vi[b] - vi[a-1];
}
avg/= b-a+1;
long double res = 0.0;
REP(i, a, b+1){
res += (vals[i]-avg)*(vals[i]-avg);
}
res/= b-a+1;
cout << fixed << setprecision(20) << res << endl;
}
return 0;
}
