#include<bits/stdc++.h>
#pragma GCC optimize(2)
#pragma GCC optimize(3,"Ofast","inline")
#define ll long long
#define I return
#define Love 0
#define Luogu ;
using namespace std;
ll n,x,a[200009],ans=0;
inline int read(){
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
    	if(ch=='-')f=-1;
    	ch=getchar();
	}
	while(ch>='0'&&ch<='9') x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
	return x*f;
}
inline void write(int x){
    if(x<0) x=~x+1,putchar('-');
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
int main(){
	n=read();
	x=read();
	for(int i=1;i<=n;i++) a[i]=read();
	for(int i=2;i<=n;i++){
		if(a[i]+a[i-1]>x){
			ans+=a[i]+a[i-1]-x;
			a[i]=a[i]-(a[i]+a[i-1]-x);
		}
	}
	write(ans);
	I Love Luogu
}