#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vl vector<ll>
#define ff(aa, bb, cc) for(ll aa = bb; aa < cc; aa++)
#define pb push_back
#define all(aaa) aaa.begin(), aaa.end()
#define rall(aaa) aaa.rbegin(), aaa.rend()
#define pll pair<ll, ll>
#define fi first
#define se second
#define ed "\n"
int main(){
ll n, k;
cin >> n >> k;
vl arr(n);
ll c = 0, maxx = 0, cur = 0, minn = LLONG_MAX;
ff(i, 0, n){
cin >> arr[i];
c += arr[i];
cur += arr[i];
if(cur < 0) cur = 0;
maxx = max(maxx, cur);
minn = min(minn, arr[i]);
}
maxx = max(maxx, cur);
if(k == n || minn >= 0){ cout << c; return 0;}
if(k == 1){ cout << maxx; return 0;}
if(minn < 0) cout << c-minn;
}
