#include <bits/stdc++.h>
using namespace std;
#define f(r,o) for(long long i=r;i<=o;++i)
long long n,x;
long long a[100010];
long long u;
signed main(){
	scanf("%lld %lld",&n,&x);
	f(1,n){
		scanf("%lld",&a[i]);
	}
	f(2,n){
		if(a[i]+a[i-1]>x){
			u+=(a[i]+a[i-1])-x;
			a[i]=x-a[i-1];
		}
	}
	printf("%lld",u);
	return 0;
}

悬关