#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <atcoder/modint>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<998244353>;

int main(){
    int N, K; cin >> N >> K;
    vector<i64> A(N); rep(i,N) cin >> A[i];
    i64 offset = 0;
    for(auto& a : A) if(a > 0){ offset += a; a = -a; }
    sort(A.rbegin(), A.rend());
    priority_queue<pair<i64, int>> que;
    vector<i64> B(N+1);
    rep(i,N) B[i+1] = A[i];
    que.push({ offset + B[1], 1 });
    vector<i64> res;
    res.push_back(offset);
    while(que.size()){
        if((int)res.size() > K) break;
        auto [p, d] = que.top(); que.pop();
        res.push_back(p);
        if(d != N){
            que.emplace(p + B[d+1] - B[d], d+1);
            que.emplace(p + B[d+1], d+1);
        }
    }
    cout << (res[K-1]) << endl;
    return 0;
}