#include<bits/stdc++.h>
using namespace std;
int a[1000086];
int main(){
	int n, x, ans = 0;
	cin >> n >> x;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
	}	
	for(int i = 1; i <= n; i++){
		if(a[i-1] + a[i] > x){
			ans += a[i - 1] + a[i] - x;
			a[i] -= a[i - 1] + a[i] - x;
		}
	}
    cout << ans;
	return 0;
}