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#include <iostream>
//#include <chrono>
//#include <fstream>
//#include <bits/stdc++.h>
#include <vector>

#define mp make_pair
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

int n, k;
vector<int> vec;

bool check(int len) {
    int count = 0;
    int in = 0;
    int cur_sum = 0;
    while (in < vec.size()) {
        cur_sum += vec[in];
        if (cur_sum >= len) {
            count++; cur_sum = 0;
        }
        in++;
    }
    return count + 1 >= k;
}

int main() {
    /*ifstream cin("in.txt");
    ofstream cout("out.txt");
    auto start_time = chrono::high_resolution_clock::now();*/

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);


    cin >> n >> k;
    vec.assign(n - 1, 0);

    int prev; cin >> prev;
    int l = 0, r = prev;
    for (int i = 0; i < n - 1; i++) {
        cin >> vec[i];
        swap(prev, vec[i]);
        vec[i] = prev - vec[i];
    }
    r = prev - r + 1;

    while (l + 1 < r) {
        int mid = (l + r) / 2;
        if (check(mid))
            l = mid;
        else
            r = mid;
    }
    cout << l << "\n";

    /*auto end_time = chrono::high_resolution_clock::now();
    chrono::duration<double> duration = end_time - start_time;
    cout << duration.count() << "\n";
    cin.close();
    cout.close();*/
    return 0;
}