#include<iostream>
using namespace std;
typedef long long ll;
const int N = 1e5+5;
ll a[N];
int n,k; 
bool check(ll x)
{
	ll t=0,day=1;
	for(int i=0;i<n;i++)
	{
		if(t+a[i]>x) t=0,day++;
		t+=a[i];
	}
	return day <= k;
}
int main()
{
	ll l=0,r=0,ans;
	cin>>n>>k;
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
		a[i]*=a[i];
		r+=a[i];
		l=max(l,a[i]);
	}
	while(l<=r)
	{
		ll mid=(l+r)/2;
		if(check(mid)) ans=mid,r=mid-1;
		else l=mid+1;
		
	}
	cout<<ans;
	return 0;
}