#include <bits/stdc++.h>
#define f first
#define s second
#define ll long long
#define pb push_back
#define all(v) v.begin(),v.end()
#define ld long double
using namespace std;
void data() {
#ifdef NURS
freopen("main.in", "r", stdin);
freopen("main.out", "w", stdout);
#endif
}
void win()
{
ios_base::sync_with_stdio(0),
cin.tie(0),cout.tie(0);
}
int block = 400;
const ld eps = 1e-6;
const int N = 1e6 + 500;
const int mod = 1e9 + 7;
const ll hh = 100010683;
const ll hh2 = 150005819;
int n, k, g, pos;
int a[N];
ll s;
int main()
{
data();
win();
cin >> n >> k;
bool was = 0;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
was = was | (a[i] < 0), s += a[i];
if (a[i] < 0)
g++, pos = i;
}
//first subtask
if (was == 0)
{
cout << s << '\n';
return 0;
}
//second subtask
if (g == 1 && k >= 2)
{
cout << s - a[pos] << '\n';
return 0;
}
else if (g == 1 && k == 1)
{
cout << s;
return 0;
}
}
