#include <iostream>
using namespace std;
int ans;

int main(){
	int n,x;
	std::ios::sync_with_stdio(false);
	int nums[int(1e5+5)];
	cin>>n>>x;
	for(int i = 1;i<=n;i++){
		cin>>nums[i];
	}
	for(int i = 1,sum;i<=n-1;i++){
		sum = nums[i]+nums[i+1];
		if(sum>x){
			while(sum>x&&nums[i+1]!=0){
				nums[i+1]--;
				sum--;
				ans++;
			}
			while(sum>x&&nums[i]!=0){
				nums[i]--;
				sum--;
				ans++;
			}
		}
	}
	cout<<ans;
	return 0;
}