#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int ar[105], cnt[105];

int main() {
    int n, ans;
    cin >> n;
    for( int i=0; i<n; i++ ) {
        cin >> ar[i];
        cnt[ ar[i] ]++;
    }
    for( int i=0; i<101; i++ ) {
        for( int j=0; j<101; j++ ) {
            if( i == j ) continue;
            if( abs( i - j ) <=1 ) ans = max( ans, cnt[i] + cnt[j] );
        }
    }
    cout << ans << "\n";
    return 0;
}