#include <fstream>

using namespace std;

ifstream f("transport.in");
ofstream g("transport.out");

float s,k,ma;
int v[16001],i,n,ss;

int main()
{
   f>>n>>k;
   for (i=1;i<=n;i++)
    {
        f>>v[i];
        s+=v[i];
    }
    s=ma=s/k;

    for (i=1;i<=n;i++)
     {
         if (ss+v[i]<=s)
          ss+=v[i];
         else
         {
             if (ss+v[i]-s>s-ss-v[i])
              ss+=v[i];
             else
              {
                  i--;
                  ss=0;
              }
              if (ss>ma)
              ma=ss;
              ss=0;
         }
     }
     g<<ma;
    f.close();
    g.close();

}