#include <bits/stdc++.h>
#define forn(i, n) for(int i = 0; i < (int)(n); i++)
typedef long long ll;
using namespace std;

const int MAXN = 100;
int a[MAXN + 1];

int main() {
    //ios_base::sync_with_stdio(false);
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);

    int n;
    cin >> n;
    for(int i = 1; i <= n; i++)
        cin >> a[i];
    int ans = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = i + 1; j <= n; j++) {
            int _min = a[i], _max = a[i], res = 1;
            if(abs(a[i] - a[j]) <= 1)
                _min = min(_min, a[j]), _max = max(_max, a[j]), res = 2;
            for (int k = j + 1; k <= n; k++) {
                if (abs(a[k] - _min) <= 1 && abs(a[k] - _max) <= 1)
                    _min = min(_min, a[k]), _max = max(_max, a[k]), res++;
            }
            ans = max(ans, res);
        }
    }
    cout << ans;
    return 0;
}