// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target ("avx,avx2,fma")
#include <bits/stdc++.h>

using std::cin, std::cout, std::cerr;
using ll = long long;

int main() {
    std::ios::sync_with_stdio(false);
    int n, p; cin >> n >> p;
    std::vector<int> a(n);
    for(int i = 0; i < n; i ++)
        cin >> a[i];
    ll inf = 1e18L;
    ll f[2] = {0, inf};
    for(int i = 1; i < n; i ++) {
        ll g[2] = {inf, inf};
        g[0] = g[1] = std::min(f[0], f[1]) + p;
        g[0] = std::min(g[0], f[0] + std::max(0, a[i] - a[i - 1]));
        g[1] = std::min(g[1], f[1] + std::max(0, a[i - 1] - a[i]));

        f[0] = g[0];
        f[1] = g[1];
    }
    cout << std::min(f[0], f[1]) << '\n';
}