#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("transport.in");
ofstream fout("transport.out");
int n,m,k,s,mx,v[1000001];
int transport(int x)
{
    int s=0,nr=1;
    for(int i=1;i<=n;i++)
    {
        if(x>=s+v[i])s+=v[i];
        else{
            nr++;
            s=v[i];
        }
    }
    //cout<<x<<" "<<nr<<endl;
    return nr;
}
int cb(int mx, int s, int k)
{
   int mij=(mx+s)/2;
   if(mx>s)return -1;
   if(transport(mij)==k)return mij-1;
   if(transport(mij)>k)
   {
     return cb(mij+1,s,k);
   }
    return cb(mx,mij-1,k);
}
int main()
{
    int i,j;
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>v[i];
        s+=v[i];
        mx=max(mx,v[i]);
    }
    fout<<cb(mx,s,k);
    return 0;
}