#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 110000;
LL a[N], s[N];
int n, F;
bool pd(LL x)
{
    s[0] = 0; for(int i = 1; i <= n; i++) s[i] = s[i-1] + a[i] - x;
    LL v = LL(1) << 62;
    for(int i = F; i <= n; i++)
    {
        v = min(v, s[i - F]);//v= min( s[0].. s[i-F] ) 
        if( s[i] - v >= 0 ) return true;
    }
    return false;
}
int main()
{
    scanf("%d%d", &n, &F);
    LL l = 0, r = 0;
    for(int i = 1; i <= n; i++) scanf("%lld", &a[i]), a[i] = a[i] * 1000, r += a[i];
    LL ans = -1;
    while(l <= r)
    {
        LL mid = (l + r) / 2;
        if( pd(mid) ){ ans = mid; l = mid + 1;}
        else r = mid - 1;
    }
    printf("%lld\n", ans);
    return 0;
}