#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e7+19;
signed main(){
	int n,x;
	cin >> n >> x;
	int ans = 0;
	int a[N];
	for (int i = 1;i <= n;i++)cin >> a[i];
	for (int i = 2;i <= n;i++){
		int lsum = a[i]+a[i-1];
		if (lsum > x){
			int dis = lsum - x;
			a[i] -= dis;
			ans += dis;
		}
	}
	cout << ans;
}

subtask 1未过