#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5 + 5;
int n, p, h[N], dp[N][2], f[N];
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cin >> n >> p;
    for (int i = 1; i <= n; i++) cin >> h[i];
    dp[1][1] = p;
    for (int i = 2; i <= n; i++) {
    	dp[i][0] = min(dp[i - 1][0] + max(0ll, h[i] - h[i - 1]), f[i - 1] + p);
    	dp[i][1] = min(dp[i - 1][1] + max(0ll, h[i - 1] - h[i]), f[i - 1] + p);
    	f[i] = min(dp[i][0], dp[i][1]);
	}
	cout << f[n]; 
    return 0;
}