//satyaki3794
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define MOD (1000000007LL)
#define LEFT(n) (2*(n))
#define RIGHT(n) (2*(n)+1)

using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;

ll pwr(ll base, ll p, ll mod = MOD){
ll ans = 1;while(p){if(p&1)ans=(ans*base)%mod;base=(base*base)%mod;p/=2;}return ans;
}


ll gcd(ll a, ll b){
    if(b == 0)  return a;
    return gcd(b, a%b);
}



int cnt[105];

int main(){

    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n;
    cin>>n;

    for(int i=1;i<=n;i++){
    	int a;
    	cin>>a;
    	cnt[a]++;
    }


    int ans = 0;
    for(int i=1;i<=100;i++){
    	ans = max(ans, cnt[i]+cnt[i+1]);
    }

    cout<<ans;
    return 0;
}