Codeforces #494 C.Intense Heat

#include<bits/stdc++.h>
using namespace std;
double dp[5005][5005];
double ans = 0;
int main(){int n,tk;cin >> n>>tk;for (int i=1;i<=n;i++){cin >> dp[i][1];}for (int i=1;i<=n;i++){for (int k = 1;i-k>=-1;k++){dp[i][k] = dp[i - 1][k - 1]  + dp[i][1];if(k>=tk && ((double)dp[i][k]/k)>ans)ans = (double)dp[i][k]/k;}}cout <<setprecision(10)<<ans;
}