#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template<class T> bool cmin(T &i, T j) { return i > j ? i=j,true:false; }
template<class T> bool cmax(T &i, T j) { return i < j ? i=j,true:false; }
mt19937 mrand(chrono::steady_clock::now().time_since_epoch().count());
uniform_int_distribution<int> ui(0, 1 << 30);
int rng() {
return ui(mrand);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n,k;
cin >> n >> k;
vector<int> v(n);
for (int &x: v)
cin >> x;
vector<array<pair<ll,ll>,2>> dp(n);
auto solve = [&](ll pen) {
dp[0][1] = {v[0] - pen,1};
dp[0][0] = {0,0};
for (int i=1;i<n;i++) {
dp[i][1] = max<pair<ll,ll>>({dp[i-1][1].first + v[i],dp[i-1][1].second},
{dp[i-1][0].first + v[i] - pen,dp[i-1][0].second + 1});
dp[i][0] = max(dp[i-1][0],dp[i-1][1]);
}
return max(dp[n-1][0],dp[n-1][1]);
};
ll lo = 0, hi = 1LL << 60;
while(lo < hi) {
ll mid = lo + (hi - lo + 1) / 2;
if (solve(mid).second >= k)
lo = mid;
else
hi = mid - 1;
}
cout << solve(lo).first + lo * k << "\n";
}
