#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<vector>
using namespace std;
int main() {
	int n, x, sum = 0;
	cin >> n >> x;
	vector<int>v;
	for (int i = 0; i < n; i++) {
		int temp;
		cin >> temp;
		v.push_back(temp);
	}
	for (int i = 1; i < n; i++) {
		while (v[i] + v[i - 1] > x) {
			if (v[i] == 0)v[i - 1]--;
			else v[i]--;
			sum++;
		}
	}
	cout << sum;
}