#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<int> A( N );
	for( int i = 0; i < N; i++ ) {
		cin >> A[i];
	}

	sort( A.begin(), A.end() );
	priority_queue<int, vector<int>, greater<int>> que;
	que.push( A[0] );
	for( int i = 1; i < N; i++ ) {
		int a = que.top();
		if( A[i] > a + 1 ) {
			que.pop();
			que.push( A[i] );
		}
		else {
			que.push( A[i] );
		}
	}
	int ans = que.size();

	cout << ans << endl;
}