#include <bits/stdc++.h>
using namespace std;
typedef long long llong;
const int MAXN = 3e5 + 10;
llong n, k;
llong a[MAXN];
pair < llong, llong > dp[MAXN][2];
void read()
{
cin >> n >> k;
for(int i = 1; i <= n; i++)
{
cin >> a[i];
}
}
pair < llong, int > check(llong x)
{
dp[1][0] = {0, 0};
dp[1][1] = {a[1] - x, 1};
for(int i = 2; i <= n; i++)
{
dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
pair < llong, llong > opt1 = {dp[i - 1][0].first + a[i] - x, dp[i - 1][0].second + 1};
pair < llong, llong > opt2 = {dp[i - 1][1].first + a[i], dp[i - 1][1].second};
dp[i][1] = max(opt1, opt2);
}
return max(dp[n][0], dp[n][1]);
}
void solve()
{
llong ans = 0;
llong left = -1;
llong right = 1e18;
llong mid;
while(right - left > 1)
{
mid = left + (right - left) / 2;
if(check(mid).second >= k)
left = mid;
else
right = mid;
}
cout << check(left).first + (llong)left * k << endl;
}
int main()
{
read();
solve();
return 0;
}
