#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, p;
    cin >> n >> p;
    vector<int> a(n), b;
    b.reserve(n);
    for(int i = 0; i < n; i++){
        cin >> a[i];
        while(b.size() >= 2 && 
              ((b.rbegin()[1] >= b.back() && b.back() >= a[i]) 
              || (b.rbegin()[1] <= b.back() && b.back() <= a[i]))){
            b.pop_back();
        }
        b.emplace_back(a[i]);
    }
    b.insert(b.begin(), a[0]);
    b.push_back(a.back());
    n = b.size();
    vector<ll> dp(n, 1ll << 60);
    dp[0] = 0;
    for(int i = 0; i + 1 < n; i++){
        dp[i + 1] = min(dp[i + 1], dp[i] + max(0, b[i + 1] - b[i]));
        dp[i + 1] = min(dp[i + 1], dp[i] + p);
        if(i + 2 < n) dp[i + 2] = min(dp[i + 2], dp[i] + p);
    }
    cout << dp.back() << '\n';
}