#include<bits/stdc++.h>
using namespace std;
long long can[100005];
int main(){
	long long n,x,count=0;
	cin>>n>>x;
	for(int i=1;i<=n;i++){
		cin>>can[i];
		if(can[i]>x){
			count+=(can[i]-x);
			can[i]=x;
		}
	}
	for(int i=2;i<=n;i+=2){
		long long p=max(can[i-1],can[i+1]);
		long long xx=can[i]+p,yy;
		if(xx>x){
			yy=xx-x;
			count+=yy;
		}
	}
	cout<<count;
	return 0;
}