#include<iostream>
#include<algorithm>
using namespace std;
int N;
long A[2<<17];
long ans;
int cnt[2<<17];
main()
{
	cin>>N;
	for(int i=0;i<N;i++)cin>>A[i];
	sort(A,A+N);
	for(int i=N;i--;)
	{
		if(A[i+1]==A[i]+2)cnt[i]=cnt[i+1]+1;
		else if(A[i+2]==A[i]+2)cnt[i]=cnt[i+2]+1;
		else cnt[i]=1;
	}
	for(int i=0;i<N;i++)
	{
		ans++;
		if(A[i]+1==A[i+1])ans+=cnt[i+1];
	}
	cout<<ans<<endl;
}