#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
signed main() {
cin.tie(0)->sync_with_stdio(0);
int n,k;
cin >> n >> k;
vector<int>a(n+1);
for(int i = 1; i<=n; i++){
cin >> a[i];
}
auto aliens = [&](int lambda) -> pii {
vector<vector<pii>>dp(n+1,vector<pii>(2));
dp[0][1] = {-(int)1e18,0};
for(int i = 1; i<=n; i++){
dp[i][1] = max(pii{dp[i-1][0].first+a[i]-lambda,dp[i-1][0].second+1},pii{dp[i-1][1].first+a[i],dp[i-1][1].second});
dp[i][0] = max(dp[i-1][0],dp[i-1][1]);
}
return max(dp[n][0],dp[n][1]);
};
int low = -1; int high = (int)1e18;
while(low + 1 < high){
int mid = (low+high)/2;
auto [cost,used] = aliens(mid);
if(used <= k){
high = mid;
}
else{
low = mid;
}
}
auto [cost,used] = aliens(high);
//cout << cost << ' ' << used << ' ' << high << '\n';
cout << cost + k * high << '\n';
return 0;
}
