#include<stdio.h>
long long n,i,j;
long long a[1000001],x,count,gap;
int main()
{
	scanf("%lld%lld",&n,&x);
	for(i=0;i<=n-1;i++)
	{
		scanf("%lld",&a[i]);
	}
	for(i=0;i<=n-1;i++)
	{
		if(a[i]+a[i+1]>x)
		{
			if(a[i]>x)
			{
				count+=x-a[i];
				a[i]=x;
			}
			gap=x-a[i];
			count+=a[i+1]-gap;
			a[i+1]=x-a[i];
		}
	}
	printf("%lld",count);
	return 0;
 }