/* You lost the game. */

#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <cfloat>
#include <numeric>
#include <cassert>
#include <unordered_set>
#include <unordered_map>
#include <fstream>
#include <vector>

#define fin(i,n) for (int i = 0; i < n; i++)
#define fin2(i,a,b) for (int i = a; i < b; i++)

#define mp make_pair
#define pb push_back

#define si(n) scanf("%d", &n)
#define sii(n,m) scanf("%d %d", &n, &m)
#define siii(n,m,k) scanf("%d %d %d", &n, &m, &k)
#define sl(n) scanf("%lld", &n)
#define sll(n,m) scanf("%lld %lld", &n, &m)
#define slll(n,m,k) scanf("%lld %lld %lld", &n, &m, &k)
#define ss(s) scanf("%s", s)

#define pi(n) printf("%d\n", n)
#define pii(n,m) printf("%d %d\n", n, m)
#define pl(n) printf("%lld\n", n)
#define pll(n,m) printf("%lld %lld\n", n, m)

#define L long long int
#define PII pair<int, int>
#define VPII vector<PII>
#define VL vector<L>
#define VI vector<int>
#define VVI vector<VI>

using namespace std;

int main() {
    int n,t, tab[1000] = {};
    si(n);
    fin(i, n) { si(t); tab[t]++; tab[t+1]++; }
    int m = 0;
    fin(i, 102) { m = max(m, tab[i]); }
    pi(m);
    return 0;
}