#include<bits/stdc++.h> 
using namespace std;
long long a[1000005];
int main()
{	
	long long m,n,x,count=0;
	for(long long i=1;i<=n;i++){
		cin>>x;
		a[x]++;
		if(x==1){
			a[x+1]++;
			a[x+2]++;
			break;
		}
		if(x==2){
			a[x+1]++;
			a[x+2]++;
			a[x-1]++;
			break;
		}
		if(x==n-1){
			a[x-1]++;
			a[x-2]++;
			a[x+1]++;break;
		}
		if(x==n){
			a[x-1]++;
			a[x-2]++;break;
		}
		a[x-1]++;
			a[x-2]++;
			a[x+1]++;a[x+2]++;
	}
	for(long long i=1;i<=n;i++){
		if(a[i]>=1)
		count++;
	}
	cin>>count;
	return 0;
	
}