#include<bits/stdc++.h>
using namespace std;
int n,x,a[1000000],ans;
int main() {
	cin>>n>>x;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=2;i<=n;i++){
		while(a[i]+a[i-1]>x){
			a[i]--;
			ans++;
		}
	}
	cout<<ans;
	return 0;
}