#include<bits/stdc++.h>
#define int long long
using namespace std;
pair<int, int> solve_lambda(int n, int a[], int lmb) {
pair<int, int> dp[n][2];
dp[0][0] = {0, 0};
dp[0][1] = {a[0] - lmb, 1};
for (int i = 1; i < n; i++) {
dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
dp[i][1] =
max(make_pair(dp[i - 1][0].first + a[i] - lmb, dp[i - 1][0].second + 1),
make_pair(dp[i - 1][1].first + a[i], dp[i - 1][1].second));
}
return max(dp[n - 1][0], dp[n - 1][1]);
}
signed main(){
int n,k;
cin >> n >> k;
int a[n];
for(int i = 0; i < n;++i){
cin >> a[i];
}
int l = 0,r = 1e18;
while(l < r){
int mid = (l+r+1)/2;
pair<int,int> ans = solve_lambda(n,a,mid);
if(ans.second >= k){
l = mid;
}else if(ans.second < k){
r = mid-1;
}
}
cout << solve_lambda(n,a,l).first + l*k;
}
