#include "bits/stdc++.h"
using namespace std;
#define sz(x) int(x.size())
#define mp make_pair
const int64_t oo = 1e16;
int main(void) {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int N, K;
cin >> N >> K;
vector<int>a(N);
for(int i = 0; i < N; i++) {
cin >> a[i];
}
auto check = [&](int64_t amt) {
pair<int64_t, int>dp[N][2];
dp[0][0] = mp(0, 0);
dp[0][1] = mp(a[0] - amt, 1);
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].first + a[i] - amt, dp[i - 1][0].second + 1),
mp(dp[i - 1][1].first + a[i], dp[i - 1][1].second));
}
return max(dp[N - 1][1], dp[N - 1][0]);
};
int64_t lo = 0, hi = oo;
while(lo < hi) {
int64_t mid = (lo + hi + 1) / 2;
check(mid).second >= K ? lo = mid : hi = mid - 1;
}
auto [c, d] = check(lo);
cout << c + d * lo << '\n';
return 0;
}
