#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
int main()
{
	int n, topIndex = 0;
	cin >> n; 
	vector<int> a;
	for (int i = 0; i < n; i++)
	{
		int ai;
		cin >> ai;
		if (i != 0)
		{
			if (abs(ai - a[topIndex]) != 1)
			{
				a.push_back(ai);
				topIndex++;
			}
			else
			{
				if (a[topIndex] < ai)
				{
					a[topIndex] = ai;
				}
			}
		}
		else
		{
			a.push_back(ai);
		}
	}
	
	cout << a.size() << endl;
	return 0;
}