#include <bits//stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_multiset;
#define ll long long
#define ld long double
#define iloop(m, h) for (ll i = m; i != h; i += (m < h ? 1 : -1))
#define jloop(m, h) for (auto j = m; j != h; j += (m < h ? 1 : -1))
#define kloop(m, h) for (auto k = m; k != h; k += (m < h ? 1 : -1))
#define lloop(m, h) for (auto l = m; l != h; l += (m < h ? 1 : -1))
#define iloop_(m, h, g) for (auto i = m; i != h; i += g)
#define jloop_(m, h, g) for (auto j = m; j != h; j += g)
#define kloop_(m, h, g) for (auto k = m; k != h; k += g)
#define lloop_(m, h, g) for (auto l = m; l != h; l += g)
#define getchar_unlocked _getchar_nolock // comment before submission
#define pll pair<ll, ll>
#define plll pair<ll, pll>
#define pllll pair<pll, pll>
#define vll vector<ll>
#define qll queue<ll>
#define dll deque<ll>
#define pqll priority_queue<ll>
#define gll greater<ll>
#define INF 1000000000000000
#define MOD1 1000000007
#define MOD2 998244353
#define MOD3 1000000009
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n, t;
cin >> n >> t;
ll a[n];
iloop(0, n) cin >> a[i];
ll lb = 0, ub = 1e16, mid;
while (ub > lb) {
mid = (lb + ub)>>1;
pll dp[n][2];
dp[0][0] = {0, 0};
dp[0][1] = {a[0]-mid, 1};
iloop(1, n) {
jloop(0, 2) {
if (j == 0) {
if (dp[i-1][0].first > dp[i-1][1].first) dp[i][0] = dp[i-1][0];
else dp[i][0] = dp[i-1][1];
}
else {
if (dp[i-1][0].first - mid > dp[i-1][1].first) dp[i][1] = {dp[i-1][0].first - mid + a[i], dp[i-1][0].second + 1};
else dp[i][1] = {dp[i-1][1].first + a[i], dp[i-1][1].second};
}
}
}
pll x = max(dp[n-1][0], dp[n-1][1]);
if (x.second > t) lb = mid + 1;
else ub = mid;
}
pll dp[n][2];
dp[0][0] = {0, 0};
dp[0][1] = {a[0]-lb, 1};
iloop(1, n) {
jloop(0, 2) {
if (j == 0) {
if (dp[i-1][0].first > dp[i-1][1].first) dp[i][0] = dp[i-1][0];
else dp[i][0] = dp[i-1][1];
}
else {
if (dp[i-1][0].first - lb > dp[i-1][1].first) dp[i][1] = {dp[i-1][0].first - lb + a[i], dp[i-1][0].second + 1};
else dp[i][1] = {dp[i-1][1].first + a[i], dp[i-1][1].second};
}
}
}
pll x = max(dp[n-1][0], dp[n-1][1]);
cout << x.first + lb*t;
}
