#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) REP(i,0,n)
#define REP(i,s,e) for(int i=(s); i<(int)(e); i++)
#define repr(i, n) REPR(i, n, 0)
#define REPR(i, s, e) for(int i=(int)(s-1); i>=(int)(e); i--)
#define all(r) r.begin(),r.end()
#define rall(r) r.rbegin(),r.rend()

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;

const ll INF = 1e18;
const ll MOD = 1e9 + 7;

template<typename T> T chmax(T& a, const T& b){return a = (a > b ? a : b);}
template<typename T> T chmin(T& a, const T& b){return a = (a < b ? a : b);}

int main(){
    ll n, p;
    cin >> n >> p;
    vl h(n);
    rep(i, n) cin >> h[i];
    vl left(n);
    iota(all(left), 0);
    REP(i, 1, n) if(h[i-1] <= h[i]) left[i] = left[i-1];
    vl dp(n, INF);
    dp[0] = 0LL;
    REP(i, 1, n) {
        chmin(dp[i], dp[i-1]+max(0LL, h[i]- h[i-1]));
        {
            int j = (left[i] == 0 ? 0 : left[i]-1);
            chmin(dp[i], dp[j]+p);
        }
    }
    cout << dp.back() << '\n';
    return 0;
}