//
//
//  Codeforces: ganariya
//  AtCoder: ganariya2525
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//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <unordered_map>
#include <climits>
#include <set>
#include <unordered_set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <random>
#include <complex>
#include <regex>
#include <locale>
#include <random>
#include <type_traits>

using namespace std;

#define SHOW_VECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOW_MAP(v){std::cerr << #v << endl; for(const auto& xxx: v){std::cerr << xxx.first << " " << xxx.second << "\n";}}

using LL = long long;

//~~~~~~~~~~~~~~~~~~~~~_(＾～＾ ｣ ∠)_~~~~~~~~~~~~~~~~~~~~~


int main() {

    LL N, L;
    cin >> N >> L;

    vector<LL> a(N);
    for (int i = 0; i < N; i++) cin >> a[i];

    vector<pair<LL, LL>> b(N);
    for (int i = 0; i < N; i++) b[i] = make_pair(a[i], i);
    sort(b.rbegin(), b.rend());

    vector<LL> dp(N, 0);
    for (int i = 0; i < N; i++) {
        int pos = b[i].second;
        LL d = 0;
        for (int j = -1; j <= 1; j += 2) {
            int to = pos + j;
            if (to < 0 || to >= N) continue;
            d = max(d, dp[to]);
        }
        dp[pos] = d + L - b[i].first;
    }

    cout << *max_element(dp.begin(), dp.end()) << endl;

}







































Measured memory_bytes: 5988