#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;
#define REP(k,a) for(int k=0; k < (a); ++k)

int main(){
    int n,tmp, ans = 0;
	scanf("%d",&n);
	vector<int> v(103);
	REP(i,n)
	{
		scanf("%d",&tmp);
		v[tmp]++;
	}

	REP(i,102) 
	{
		int tmp= v[i] + v[i+1];
		ans = max<int> (ans,tmp);
	}
	printf("%d\n",ans);
	return 0;
}