#include<iostream>
#include<algorithm>
#include<iomanip> 
#include<stdio.h>
using namespace std;
	const long long MAX=1e5;
int main(){
	long long a[MAX];
	long long b=0,n,x;
	cin>>n>>x;
	for(int i=0;i<n;i++){
		cin>>a[i];
		if(i%2!=0){
			if(a[i]+a[i-1]>x||a[i]+a[i+1]>x){
				b=b+a[i]+max(a[i-1],a[i+1])-x;
			}
		}
	}
	cout<<b;
	return 0;
}