#include<cstdio>

 #include<algorithm>

 #include<vector>

 #include<queue>

 #include<map>

 #include<iostream>

 #include<cstring>

 using namespace std;

 #define Fopen freopen("_in.txt","r",stdin); freopen("_out.txt","w",stdout);

 #define LL long long

 #define ULL unsigned LL

 #define fi first

 #define se second

 #define pb push_back

 #define lson l,m,rt<<1

 #define rson m+1,r,rt<<1|1

 #define lch(x) tr[x].son[0]

 #define rch(x) tr[x].son[1]

 #define max3(a,b,c) max(a,max(b,c))

 #define min3(a,b,c) min(a,min(b,c))

 typedef pair<int,int> pll;

 const int inf = 0x3f3f3f3f;

 const LL INF = 0x3f3f3f3f3f3f3f3f;

 const LL mod =  (int)1e9+;

 const int N = 1e5 + ;

 int n, f;

 int a[N];

 LL suf[N];

 bool check(int mid){

     for(int i = ; i <= n; ++i)

         suf[i] = suf[i-] + a[i] - mid;

     LL minval = ;

     for(int i = f; i <= n; ++i){

         minval = min(minval, suf[i-f]);

         if(suf[i] - minval >= ) return true;

     }

     return false;

 }

 int main(){

     scanf("%d%d", &n, &f);

     for(int i = ; i <= n; ++i)

         scanf("%d", &a[i]), a[i] *= ;

     int l = , r = inf;

     while(l <= r){

         int m = l+r >> ;

         if(check(m)) l = m + ;

         else r = m - ;

     }

     printf("%d\n", l-);

     return ;

 }