//#include<bits/stdc++.h>
#include<iostream>
#include<math.h>
#include<cstring>
#include<string.h>
#include<algorithm>
#include<stdio.h>
using namespace std;
int n,x,a[100005],sum; 
int main()
{
	cin>>n>>x;
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
	}
	for(int i=0;i<n-1;i++)
	{
		if(a[i]+a[i+1]<=x)
		{
			continue;
		}
		while(a[i]+a[i+1]>x)
		{
			if(a[i]!=0)
			{
				a[i]--;
				sum++;
			}
			else
			{
				break; 
			}
		}
		if(a[i]+a[i+1]<=x)
		{
			continue;
		}
		while(a[i]+a[i+1]>x)
		{
			if(a[i+1]!=0)
			{
				a[i+1]--;
				sum++;
			}
			else 
			{
				break; 
			}
		}
	}
	cout<<sum; 
	return 0;
}