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

int main() {
	// your code goes here
	int n;
	cin >> n;
	int a[101],c[102] = {0};
	for(int i=0;i<n;i++)
		{cin >> a[i];
		c[a[i]]++;
		}
	int ans = 0;int maxi = 0;
	for(int i=0;i<100;i++){
		ans = 0;
		if(c[i] > 0)
		ans = c[i]+ c[i+1];
		if(ans > maxi) maxi = ans;
	}
		cout << maxi <<endl;
	
	return 0;
}