#include<bits/stdc++.h>
using namespace std;
int n,x,a[100001],s,t,ma;
int main(){
    scanf("%d%d",&n,&x);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<n;i++)
      if(a[i]+a[i+1]>x){
          t=a[i]+a[i+1];
          s += (a[i+1]-(x-a[i])),a[i+1]=x-a[i];
      }
    printf("%d",s);
    return 0;
}