#include <bits/stdc++.h>
#define fo(i,n) for(i=0;i<n;++i)
#define forr(i,n) for(i=n-1;i>=0;--i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef vector<int> vi;

ll gcd(ll a,ll b){while(a&&b)a>b?a%=b:b%=a;return a+b;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

int main(){
    int n;
    cin>>n;
    int a[n];
    int b[101] = {0};
    int i, j;
    fo(i,n)
    {
        cin>>a[i];
        b[a[i]]++;
    }
    int maxer = 2;
    for(i=1;i<=100;i++){
        if(b[i]+b[i-1] > maxer)
            maxer = b[i-1]+b[i];
    }
    cout<<maxer<<endl;
    return 0;
}