#include<bits/stdc++.h>
using namespace std;
#define task "task"
#define ii pair<int,int>
#define fi first
#define se second
#define int long long
#define ll long long
#define ld double
#define mp make_pair
#define lg2 20
#define iii pair<int,ii>
#define iiii pair<ii,ii>
#define base 29
#define eps 1e-8
int dx[]= {0LL,0LL,1,-1,1,1,-1,-1};
int dy[]= {1,-1,0LL,0LL,1,-1,1,-1};
const int maxn=5e5+5;
const int mod=1e9+7;
int n,k,a[maxn];
ii dp[maxn][2];
void init()
{
cin>>n>>k;
for(int i=1;i<=n;i++)cin>>a[i];
}
bool check(int mid)
{
dp[0][1]={-1e18,0};
for(int i=1;i<=n;i++)
{
dp[i][0]=max(dp[i-1][0],dp[i-1][1]);
dp[i][1]=max(mp(dp[i-1][0].fi+a[i]-mid,dp[i-1][0].se+1),mp(dp[i-1][1].fi+a[i],dp[i-1][1].se));
}
ii ans=max(dp[n][0],dp[n][1]);
return ans.se>=k;
}
void process()
{
int l=0,r=1e15,ans=0;
while(l<=r)
{
int mid=(l+r)/2;
if(check(mid))
{
l=mid+1;
ans=mid;
}
else r=mid-1;
}
check(ans);
ii sum=max(dp[n][0],dp[n][1]);
cout<<sum.fi+k*ans;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
if(fopen(task".inp","r"))
{
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
init();
process();
cerr <<endl<< "TIME : " << clock() * 0.001 << "s" << endl ;
}
