#include <bits/stdc++.h>
using namespace std;
int main () {
	long long n, m;
	cin >> n >> m;
	const int N = n;
	long long a[N];
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	int sum = 0;
	for (int i = 0; i < n; i++) {
		if (i == 0) {
			continue;
		} else if (a[i-1] + a[i] > m) {
			if (a[i] >= m) {
				sum += a[i]+a[i-1]-m;
				a[i] = m - a[i-1];
			} else if (a[i-1] >= m) {
				sum += a[i]+a[i-1]-m;
				a[i-1] = m - a[i];
			} else if (a[i] >= m && a[i-1] >= m) {
				sum += a[i]+a[i-1]-m;
				a[i] = m - a[i-1];
			} else {
				sum += a[i]+a[i-1]-m;
				a[i] = m - a[i-1];
			}
		}
	}
	cout << sum;
	return 0;
}