#include <bits/stdc++.h>
using namespace std;
#define endl           '\n'
#define LL             long long
#define ULL            unsigned long long
#define all(x)         x.begin(), x.end()
#define fill(a, b)     memset(a, b, sizeof a)


const LL Mod = 1000000007;
const int N = 1e5 + 5;

int cnt[123];

int main() {
    int n;
    cin >> n;
    for (int i = 1, k; i <= n; i++) {
        cin >> k;
        cnt[k]++;
    }
    int best = 0;
    for (int i = 1; i <= 100; i++) {
        best = max(best, cnt[i] + cnt[i - 1]);
    }
    cout << best << endl;
}