#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 10;
int n, m;
ll a[N];

bool check(ll x){
    ll cnt = 1;
    ll len = a[1];
    if(a[1] > x)return 0;
    for(int i = 2;i <= n;i++){
        if(a[i] > x)return 0;
        if(len + a[i] + 1 > x){
            cnt++;
            len = a[i];
        }

        else{
            len += a[i] + 1;
        }
    }
    return cnt <= m;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    ll sum = 0;
    for(int i = 1;i <= n;i++){
        cin >> a[i];
    }
    ll l = 1, r = 1e18;
    // cout << sum << endl;
    while(l < r){
        ll mid = (l + r) >> 1;
        if(check(mid))r = mid;
        else l = mid + 1;
    }
    cout << r;

    return 0;
}