#include <bits/stdc++.h>
#define MULTI int _; cin >> _; while(_--)
#define fi first
#define se second
#define pb(a) push_back(a)
#define rep(i, n) for(int i = 0; i < n; i++)
#define reps(i, n, m) for(int i = n; i <= m; i++)
#define repsv(i, n, m) for(int i = n; i >= m; i--)
#define vsz(a) (int)(a.size())
#define mp(a, b) make_pair(a, b)
#define all(a) a.begin(), a.end()

using namespace std;

typedef pair<double, double> pdd;
typedef pair<int, int> pii;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef long long int ll;
typedef long double ld;
typedef vector<ll> vll;

#ifdef LOCAL
#include "debugs.hpp"
#else
#define dbg(...) 0
#endif

int dp[300][300];
int n, h;
vi b;

inline int save(int l, int r){
    return max(0, h+1-((b[r]-b[l])%2 ? (b[r]-b[l])/2 + 1 : (b[r]-b[l])/2));
}

int calc(int l, int r){
    if(l==r) return h;
    if(dp[l][r]!=-1)
        return dp[l][r];
    int res = INT_MAX;
    reps(m, l, r-1)
        res = min(res, calc(l, m) + calc(m+1, r) - save(l, r));
    return res;
}

void solve(){
    rep(i,300)rep(j,300)dp[i][j]=-1;
    cin >> n >> h;
    b = vi(n);
    rep(i, n)
        cin >> b[i];
    cout << calc(0, n-1) << '\n';
}

int main(){
    ios_base::sync_with_stdio(false);
    // MULTI
    solve();
}