#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define all(x) x.begin(), x.end()
#define endl "\n"
#define fi first
#define se second
using namespace std;
typedef pair<int, int> ii;
int n, k;
vector<int> a;
ii maxsub(int c) {
int n = a.size();
int t = 0, cnt = 0;
int cur = 0;
for (int i = 0; i < n; ++i) {
if (cur + a[i] - c < 0) {
cur = 0;
} else {
cur += a[i] - c;
if (cur >= 0) {
t += cur;
cnt++;
cur = 0;
}
}
}
return {t + cnt * c, cnt};
}
int32_t main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> k;
a.resize(n);
for (int i = 0; i < n; ++i) {
cin >> a[i];
}
if (k == 1) {
int cur = a[0], res = a[0];
for (int i = 1; i < n; ++i) {
cur = max(a[i], cur + a[i]);
res = max(res, cur);
}
cout << res << endl;
return 0;
}
int l = -1e10, h = 1e10;
int ans = 0;
while (l <= h) {
int mid = (l + h) / 2;
ii res = maxsub(mid);
int total = res.fi;
int num = res.se;
if (num >= k) {
ans = total - mid * k;
l = mid + 1;
} else {
h = mid - 1;
}
}
cout << ans << endl;
return 0;
}
