#include <vector>
#include <cassert>
namespace po167{

template<class T, T(*op)(T, T)>
struct Doubling_op{
    int n;
    int depth;
    std::vector<std::vector<int>> index;
    std::vector<std::vector<T>> val;
    Doubling_op(std::vector<int> p, std::vector<T> v, long long lim = (1ll << 60) - 1){
        n = p.size();
        for (auto x : p) assert(0 <= x && x < n);
        assert(n == (int)v.size());
        depth = 1;
        while ((1ll << depth) <= lim) depth++;
        index.resize(depth);
        val.resize(depth);
        index[0] = p;
        val[0] = v;
        for (int i = 1; i < depth; i++){
            index[i].resize(n);
            val[i].resize(n);
            for (int j = 0; j < n; j++){
                int tmp = index[i - 1][j];
                index[i][j] = index[i - 1][tmp];
                val[i][j] = op(val[i - 1][j], val[i - 1][tmp]);
            }
        }
    }
    std::pair<int, T> query(int start_ind, T start_val, long long times){
        assert(0 <= start_ind && start_ind < n);
        assert(0 <= times && times < (1ll << depth));
        int i = 0;
        while (times){
            if (times & 1){
                start_val = op(start_val, val[i][start_ind]);
                start_ind = index[i][start_ind];
            }
            i++;
            times >>= 1;
        }
        return std::make_pair(start_ind, start_val);
    }
};

struct Doubling{
    int n;
    int depth;
    std::vector<std::vector<int>> index;
    Doubling(std::vector<int> p, long long lim = (1ll << 60) - 1){
        n = p.size();
        for (auto x : p) assert(0 <= x && x < n);
        depth = 1;
        while ((1ll << depth) <= lim) depth++;
        index.resize(depth);
        index[0] = p;
        for (int i = 1; i < depth; i++){
            index[i].resize(n);
            for (int j = 0; j < n; j++){
                index[i][j] = index[i - 1][index[i - 1][j]];
            }
        }
    }
    int query(int ind, long long times){
        assert(0 <= ind && ind < n);
        assert(0 <= times && times < (1ll << depth));
        int i = 0;
        while (times){
            if (times & 1) ind = index[i][ind];
            i++;
            times >>= 1;
        }
        return ind;
    }
};
}




int op(int a, int b){
    return std::min(a, b);
}

#include <iostream>

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int N, K;
    std::cin >> N >> K;
    std::vector<long long> A(N);
    for (int i = 0; i < N; i++) std::cin >> A[i];
    std::vector<long long> S(N * 2 + 1);
    for (int i = 0; i < N; i++){
        S[i + 1] = S[i] + A[i];
    }
    for (int i = 0; i < N; i++){
        S[i + 1 + N] = S[i + 1] + S[N];
    }
    long long l = 0, r = (1ll << 50);
    auto f = [&](long long m) -> int {
        std::vector<int> v(N * 2 + 1);
        for (int i = 0; i < N * 2; i++){
            while (v[i] != N * 2 && S[v[i]] - S[i] < m) v[i]++;
            v[i + 1] = v[i];
        }
        v[N * 2] = N * 2;
        po167::Doubling D(v, K);
        int ok = 0;
        for (int i = 0; i < N; i++){
            if (D.query(i, K) <= N + i) ok++;
        }
        return ok;
    };
    while (r - l > 1){
        long long m = (l + r) / 2;
        if (f(m)) l = m;
        else r = m;
    }
    std::cout << l << "\n";
}