#include<bits/stdc++.h>
using namespace std;
vector<int>v;
int main()
{
  int n,k,ans=0,t;
  cin>>n>>k;
  for(int i=1;i<=n;i++)
  {
  	cin>>t;
  	v.push_back(t);
  }
  for(int i=1;i<=v.size();i+=2)
  	if(v[i]+v[i]>k)
  	  ans+=v[i]+v[i-1]-k;
  cout<<ans;
  return 0;
}

样例全过，提交全WA就离谱