#include <stdio.h>
#include <stdlib.h>

void main()
{
	FILE *dat;
	dat=fopen("Saksije.in","r");
	int n,k;
	fscanf(dat,"%d%d",&n,&k);
	int *A,i;
	A=(int *)malloc(n*sizeof(int));
	for (i=0;i<n;i++)
		fscanf(dat,"%d",A+i);
	fclose(dat);

	int suma=0;
	for (i=0;i<n-1;i++)
	{
		if (A[i]>k)
		{
			suma=(suma+A[i]-k)%1000000000;
			A[i+1]+=A[i]-k;
		}
		else
		{
			suma=(suma+k-A[i])%1000000000;
			A[i+1]-=k-A[i];
		}
	}
	
	dat=fopen("Saksije.out","w");
	fprintf(dat,"%d\n",suma);
	fclose(dat);
}