#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

const ll INF = (ll)1e18;
ll dp[200005][2];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int N, P;
    cin >> N >> P;
    vll H(N);
    rep(i, N)cin >> H[i];

    rep(i, N)rep(j, 2)dp[i][j] = INF;
    dp[0][0] = 0;
    rep(i, N - 1)rep(j, 2) {
        ll nex = dp[i][j];
        if (!j&&H[i] < H[i + 1])nex += min((ll)P, H[i + 1] - H[i]);
        if (j&&H[i] > H[i + 1])nex += min((ll)P, H[i] - H[i + 1]);
        smin(dp[i + 1][j], nex);
        smin(dp[i + 1][!j], dp[i][j] + P);
    }
    cout << min(dp[N - 1][0], dp[N - 1][1]) << endl;
}