#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define ll long long
#define len(s) (int)s.size()
#define int long long
#define pii pair<int, int>
#define fi first
#define se second
#define MASK(k) (1LL << (k))
int n, k;
const int MX = 3e5 + 5;
int a[MX];
pii dp[MX][2];
pii solve(int lmb){
// {sum with current penalty, # of arrays}
dp[1][0] = {0, 0}; //do not create new array
dp[1][1] = {a[1] - lmb, 1}; // create 1 array with penalty
for(int i=2; i<=n; ++i){
// do not do anything
dp[i][0] = max(dp[i-1][0], dp[i-1][1]);
// create new array with penalty or assign to previous array
pii p1 = {dp[i-1][0].fi + a[i] - lmb, dp[i-1][0].se + 1};
pii p2 = {dp[i-1][1].fi + a[i], dp[i-1][1].se};
dp[i][1] = max(p1, p2);
}
return max(dp[n][0], dp[n][1]);
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen("main.inp","r",stdin);
//freopen("main.out","w",stdout);
cin >> n >> k;
for(int i=1; i<=n; ++i) cin >> a[i];
int ans = 0;
for(int l=0, r=1e18; l<=r; ){
int mid = (l + r) >> 1;
pii cost = solve(mid);
if(cost.second >= k){
l = mid + 1;
ans = cost.first + mid*k;
}
else r = mid - 1;
}
cout << ans;
return 0;
}
