#include<bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;
constexpr int N=1e6+10;
constexpr int mod=998244353;
void solve()
{
    
    int n,k;
    cin >> n >> k;
    vector<int> f(n);
    int m=0;
    for(int i=0;i<n;i++)
    {
        cin >> f[i];
        m=max(m,f[i]);
    }
    int l=m;
    int r=1e18;
    int mid;
    while(l+1!=r)
    {
        mid=l+(r-l>>1);
        int tmp=1;
        int num=mid;
        for(int i=0;i<n;i++)
        {
            if(num-f[i]>=0)
            {
                num-=f[i];
                if((num==0||num==1)&&i!=n-1)
                {
                    tmp++;
                    num=mid;
                }else num--;
            }else
            {
                tmp++;
                num=mid;
                num-=f[i];
                if((num==0||num==1)&&i!=n-1)
                {
                    tmp++;
                    num=mid;
                }else num--;
            }
            
        }
        if(tmp>k)
        {
            l=mid;
        }else r=mid;
    }
    cout << r << endl;
}
signed main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    // int o;
    // cin >> o;
    // while(o--)
    solve();
    return 0;
}             
//
//⠀⠀⠀             ⠀⢸⣿⣿⣿⠀⣼⣿⣿⣦⡀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠀⠀ ⠀⢸⣿⣿⡟⢰⣿⣿⣿⠟⠁
//⠀⠀⠀⠀⠀⠀⠀⢰⣿⠿⢿⣦⣀⠀⠘⠛⠛⠃⠸⠿⠟⣫⣴⣶⣾⡆
//⠀⠀⠀⠀⠀⠀⠀⠸⣿⡀⠀⠉⢿⣦⡀⠀⠀⠀⠀⠀⠀ ⠛⠿⠿⣿⠃
//⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣦⠀⠀⠹⣿⣶⡾⠛⠛⢷⣦⣄⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣧⠀⠀⠈⠉⣀⡀⠀ ⠀⠙⢿⡇
//⠀⠀⠀⠀⠀⠀⢀⣠⣴⡿⠟⠋⠀⠀⢠⣾⠟⠃⠀⠀⠀⢸⣿⡆
//⠀⠀⠀⢀⣠⣶⡿⠛⠉⠀⠀⠀⠀⠀⣾⡇⠀⠀⠀⠀⠀⢸⣿⠇
//⢀⣠⣾⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⢀⣼⣧⣀⠀⠀⠀⢀⣼⠇ 
//⠈⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⡿⠋⠙⠛⠛⠛⠛⠛⠁
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣾⡿⠋⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⢾⠿⠋⠀
//