#include<iostream>
#include<fstream>
using namespace std;
int main()
{int n,k,i,s=0,sc1,sc2,sim=0,max=-1,cat,rest,cat1,rest1,v[1601],s1;
ifstream f("transport.in");
ofstream g("transport.out");
f>>n>>k;
for(i=1;i<=n;i++)
{f>>v[i];
s=s+v[i];
}
cat=s/k;
rest=s%k;
for(i=1;i<=n;i++)
{sim=sim+v[i];
if(sim>=cat)
{s1=sim-v[i];
sc1=s-s1;
sc2=s-sim;
k=k-1;
cat1=sc1/k;
rest1=sc1%k;
if(cat1<=cat&&rest1<=rest)
    {s=s-s1;
     if(s1>max)
         max=s1;
    }
else
    {s=s-sim;
      if(sim>max)
          max=sim;
    }
sim=0;
}
}
g<<max;
f.close();
g.close();
return 0;
}