#include<bits/stdc++.h>
using namespace std;
long long n,x,a[500005],ans=0;
int main() {
	cin>>n>>x;
	for(int i=1; i<=n; ++i) {
		cin>>a[i];
	}
	for(int i=1; i<=n; ++i) {
		while(a[i]+a[i+1]>x) {
			if(a[i+1]!=0) {
				a[i+1]--;
				ans++;
			} else {
				a[i]--;
				ans++;
			}
		}
	}
	cout<<ans;
	return 0;
}