#include <algorithm>
#include <cmath>
#include <cstdio>

using namespace std;

namespace IO {
    const int MAX_SIZE = 1 << 20;

    char buf[MAX_SIZE], *p1 = buf, *p2 = buf;
    char gc() {
        return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, MAX_SIZE, stdin), p1 == p2) ? EOF : *p1++;
    }
    template <typename T> void R(T &x) {
        x = 0;
        char ch = gc();
        while (ch < '0' || ch > '9') ch = gc();
        while (ch >= '0' && ch <= '9') {
            x = (x << 3) + (x << 1) + (ch ^ 48);
            ch = gc();
        }
    }
}  // namespace IO
using IO::R;

const long long inf = 0x3f3f3f3f3f3f3f3f;

int n, w, h1, h2;
long long p, b = inf, f;
void solve() {
    R(n), R(w), R(h1);
    for (int i = 2; i <= n; ++i) {
        R(h2);
        f = min(p, b);
        p = min(f + w, p + (h1 < h2) * (h2 - h1));
        b = min(f + w, b + (h2 < h1) * (h1 - h2));
        h1 = h2;
    }
    printf("%lld", min(p, b));
}

int main() {
    solve();
    return 0;
}