#include <bits/stdc++.h>
#define all(vec) vec.begin(), vec.end()
using namespace std;
using ll = long long;
using P = pair<int, int>;
constexpr ll INF = (1LL << 30) - 1LL;
constexpr ll LINF = (1LL << 60) - 1LL;
constexpr ll MOD = 1e9 + 7;
template <typename T> void chmin(T &a, T b) { a = min(a, b); }
template <typename T> void chmax(T &a, T b) { a = max(a, b); }
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n, p;
    cin >> n >> p;
    vector<ll> h(n);
    for (int i = 0; i < n; i++) {
        cin >> h[i];
    }
    vector<ll> dp0(n, LINF), dp1(n, LINF);
    dp0[1] = min(p, max(0LL, h[1] - h[0])), dp1[1] = p;
    for (int i = 2; i < n; i++) {
        chmin(dp0[i], min(dp0[i - 1], dp1[i - 1]) + p);
        chmin(dp1[i], min(dp1[i - 1], dp0[i - 1]) + p);
        chmin(dp0[i], dp0[i - 1] + max(0LL, h[i] - h[i - 1]));
        chmin(dp1[i], dp1[i - 1] + max(0LL, h[i - 1] - h[i]));
    }
    cout << min(dp0[n - 1], dp1[n - 1]) << endl;
}