#include<bits/stdc++.h>
using namespace std;

const long long maxn=1000000000;
long long a[maxn];

int main(){
	long long n,x,ans=0;//ans 是需要吃掉的糖果数 
	
	scanf("%lld %lld",&n,&x);
	for(int i=1;i<=n;i++){	
		scanf("%lld",&a[i]);
	}
	
	for(int i=1;i<n;i++){
			while(a[i]+a[i+1]<=x || a[i+1]>0){
				a[i+1]--;
				ans++;
			}
			if(a[i]+a[i+1]>x){
				while(a[i]+a[i+1]<=x){
					a[i]--;
					ans++;
				}
			}
	}
	
	printf("%lld",ans);
	return 0;
}

感激不尽