#include <bits/stdc++.h>
#define itn int
#define ll long long
#define retrun return
#define ull unsigned long long
using namespace std;

int in(){
	char c = getchar();
	int x = 0, f = 1;
	for (; c < '0' || c > '9'; c = getchar())
		if (c == '-') f = -1;
	for (; c >= '0' && c <= '9'; c = getchar())
		x = (x << 1) + (x << 3) + (c ^ 48);
	return x * f;
}

void pr(int x){
	if (x < 0) x = -x, putchar('-');
	if (x > 9) pr(x / 10);
	putchar(x % 10 + '0');
}

int  main(void){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int n=in(),x=in();
	int a[n+2];
	for(int i=0;i<n;i++){
		a[i]=in();
	}
	int ans=0;
	for(int i=0;i<n-1;i++){
		if(a[i]+a[i+1]>x){
			ans+=a[i]+a[i+1]-x;
			a[i+1]-=(a[i]+a[i+1]-x);
		}
	} 
	printf("%d\n", ans);
	return (0);
}