#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll a[100005];
int main()
{
	ll n,x,ans=0;
	cin>>n>>x;
	for(ll i=1;i<=n;i++)cin>>a[i];
	for(ll i=1;i<=n;i++)
	{
		if(i%2==1)
		{
			if(a[i]+a[i+1]>x)
			{
				ans+=a[i+1]-x+a[i];
				a[i+1]=x-a[i];				
			}				
		}
		else
		{
			if(a[i]+a[i+1]>x)
			{
				ans+=a[i]-x+a[i+1];
				a[i]=x-a[i+1];
			}
		}
	}
	cout<<ans;
	return 0;
}