# include <stdio.h>
# include <bits/stdc++.h>
using namespace std;
# define fi cin
# define fo cout
# define x first
# define y second
# define ll long long
# define IOS ios_base :: sync_with_stdio(0);cin.tie(0)
# define p(v) cerr << #v << " = " << v << '\n'
# define p2(v) cerr << #v << " = " << (complex < int > (v.x,v.y)) << '\n'
# define vi vector < int >
# define vl vector < ll >
# define pii pair < int , int >
# define mp make_pair
# define db long double
# define pb push_back
# define pdd pair < db , db >
int main(void)
{
    #ifdef CF
    freopen("input","r",stdin);
    #endif // CF
    srand(time(0));
    fo << fixed << setprecision(7);
    cerr << fixed << setprecision(7);
    static int s[1 << 20];
    int n;
    fi>>n;
    while (n --)
    {
        int v;
        fi>>v;
        ++s[v];
    }
    int ans = 0;
    for (int i = 1;i <= 100;++i)
        ans = max(ans,s[i] + s[i + 1]);
    fo << ans << '\n';
    cerr << "Time elapsed :" << clock() * 1000.0 / CLOCKS_PER_SEC << " ms" << '\n';
    return 0;
}