import sys
input = sys.stdin.readline

N,P=map(int,input().split())
A=list(map(int,input().split()))

USE=[0]*N
for i in range(1,N-1):
    if A[i-1]<=A[i]<=A[i+1]:
        USE[i]=1
    if A[i-1]>=A[i]>=A[i+1]:
        USE[i]=1

B=[]
for i in range(N):
    if USE[i]==0:
        B.append(A[i])

if len(B)>=2 and B[0]>=B[1]:
    B.pop(0)

ANS=0

for i in range(0,len(B),2):
    if i+1<len(B):
        ANS+=min(B[i+1]-B[i],P)

DP=[1<<63]*len(B)
DP[0]=0

for i in range(1,len(B)):
    if i%2==0:
        if i-1>=0:
            DP[i]=min(DP[i],DP[i-1]+P)
        if i-2>=0:
            DP[i]=min(DP[i],DP[i-2]+B[i-1]-B[i-2])
            DP[i]=min(DP[i],DP[i-2]+P)
    else:
        if i-1>=0:
            DP[i]=min(DP[i],DP[i-1]+P)
        if i-2>=0:
            DP[i]=min(DP[i],DP[i-2]+B[i-2]-B[i-1])
            DP[i]=min(DP[i],DP[i-2]+P)

ANS=DP[-1]
if len(B)>=2:
    ANS=min(ANS,DP[-2]+P)
if len(B)>=2:
    if len(B)%2==0:
        ANS=min(ANS,DP[-2]+B[-1]-B[-2])
    else:
        ANS=min(ANS,DP[-2])

print(ANS)