#include<bits/stdc++.h>
using namespace std;
const int MAXN=3e5+5;
int n;
long long k;
int a[MAXN];
pair<int,int> test(long long lmb) {
pair<long long, long long> 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]);
};
int main() {
cin >> n >> k;
long long ans=0;
for(int i=0;i<n;++i) cin >> a[i];
long long l=0,r=1e18;
while(l<r) {
long long mid=(l+r+1)/2;
pair<long long,long long> p=test(mid);
if(p.second>=k) {
l=mid;
if(p.second==k) {
ans=max(ans,p.first+l*k);
}
}
else {
r=mid-1;
}
}
cout << ans;
}
