#include <cstdio>
#include <vector>
#define repeat(i, n) for (int i = 0; (i) < int(n); ++(i))
using ll = long long;
using namespace std;
template <class T> inline void setmin(T & a, T const & b) { a = min(a, b); }

constexpr ll inf = ll(1e18)+9;
int main() {
    // input
    int n, p; scanf("%d%d", &n, &p);
    vector<int> h(n); repeat (i, n) scanf("%d", &h[i]);
    // solve
    ll fwd = 0;
    ll bck = inf;
    repeat (i, n - 1) {
        ll prv = min(fwd, bck);
        if (h[i] < h[i + 1]) {
            fwd += h[i + 1] - h[i];
        } else {
            bck += h[i] - h[i + 1];
        }
        setmin(fwd, prv + p);
        setmin(bck, prv + p);
    }
    ll result = min(fwd, bck);
    // output
    printf("%lld\n", result);
    return 0;
}