#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<climits>
#include<iomanip>
#include<algorithm>
#include<ctime>
using namespace std;

bool a[1000000003];
int main(){
	int n,t,b,ans=0;
	cin>>n>>t;
	for(int i=1;i<=n;i++)
	{
		cin>>b;
		memset(a+b,1,t);
	}
	for(int i=1;i<=b+t;i++)
	{
		if(a[i])
		{
			ans++;
		}
	}
	cout<<ans;
	return 0;
}