#include <bits/stdc++.h>
#define int long long
#define endl "\n"
using namespace std;
int n,k;
vector<int>a;
pair<int,int>calc(int lambda){
vector<vector<pair<int,int>>>dp(n,vector<pair<int,int>>(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;
a.resize(n);
for(int i=0;i<n;i++){
cin>>a[i];
}
int l = 0;
int r = 1000000000000000000LL;
while(l<r) {
int mid=(l+r+1)/2;
(calc(mid).second>=k?l=mid:r=mid-1);
}
cout<<calc(l).first+(l*k)<<endl;
}
