#include <bits/stdc++.h>
using namespace std;

const int N = 110;

int n, a[N];

void solve() {
    cin >> n;
    int ans = 0;
    for (int i = 1; i <= n; ++i) { int x; cin >> x; a[x]++; }
    for (int i = 1; i < 100; ++i) ans = max(ans, a[i] + a[i-1]);
    cout << ans << endl;
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    /// MULTITEST
    //int t; cin >> t;
    //while(t--)

    solve();
}