/*
TASK: Picking Numbers
LANG: C++
*/
#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define EPS 1e-9
#define ALL(x) (x).begin(),(x).end()
#define mp(x,y) make_pair((x),(y))
#define pb(x) push_back((x))
#define FOR(i,st,ed) for(int (i)=(st);(i)<(ed);(i)++)
typedef pair<int,int> PII;
typedef vector<int> vi;
typedef vector<pair<int,int> > vii;
typedef long long LL;

int N,M,T;
int co[127];
int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	//freopen("xxx.in","r",stdin);
	//freopen("xxx.out","w",stdout);
	int i,j,k;
	cin >> N;
	while(N--)
    {
        cin >> k;
        co[k]++;
    }
    int Mc=0;
    for(i=1;i<100;i++)
        Mc=max(Mc,co[i]+co[i+1]);
    cout << Mc << '\n';
	return 0;
}