#include<bits/stdc++.h>
using namespace std;
int n,x,cnt=0;
int a[1000005];
signed main(){
	cin>>n>>x;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}	
	for(int i=1;i<=n;i++){
		if(a[i-1]+a[i]>x){
			cnt+=a[i-1]+a[i]-x;
			a[i]-=a[i-1]+a[i]-x;
		}
	}
	cout<<cnt;
	return 0;
}