#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,a,b) for(int i = a; i <= b; i++)
#define per(i,a,b) for(int i = a; i >= b; i--)
#define pii pair<int,int>
#define pb push_back
#define fi first
#define se second
const int MAXN = 3e5+10;
const int INF = 1e18+10;
int a[MAXN];
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(nullptr);
int n,k; cin >> n >> k;
rep(i,1,n) cin >> a[i];
auto check = [&](int dx) {
pii dp[n][2];
dp[1][0] = {0,0};
dp[1][1] = {a[1]-dx, 1};
rep(i,2,n) {
dp[i][0] = max(dp[i-1][0], dp[i-1][1]);
dp[i][1] = max(pii(dp[i-1][0].fi + a[i]-dx, dp[i-1][0].se + 1),pii(dp[i-1][1].fi + a[i], dp[i-1][1].se));
}
return max(dp[n][0], dp[n][1]);
};
int lo = 0, hi = 1e18;
while (lo < hi) {
int mid = (lo+hi+1)/2;
check(mid).se >= k ? lo = mid : hi = mid-1;
}
cout << check(lo).fi + lo*k;
return 0;
}
