#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N, P, *H = map(int, read().split())

# 最後の 2 地点間ごとの値。jump, right, left
INF = 10 ** 18
dp = [INF, 0, INF]
for h1, h2 in zip(H, H[1:]):
    newdp = [INF, INF, INF]
    newdp[0] = min(dp) + P
    newdp[1] = min(dp[0], dp[1]) + max(0, h2 - h1)
    newdp[2] = min(dp[0], dp[2]) + max(0, h1 - h2)
    dp = newdp
print(min(dp))