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