#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> P;
int INF = 3e18;
int mod = 1e9+7;
int dx[4] = {1, 0,-1, 0};
int dy[4] = {0, 1, 0,-1};
signed main() {
    int N;
    cin >> N;
    vector<int>A(N);
    map<int,int>Mp;
    int ans = 0;
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        Mp[A[i]]++;
        ans = max(ans,Mp[A[i]]+Mp[A[i]+1]);
        ans = max(ans,Mp[A[i]]+Mp[A[i]-1]);
    }
    cout << ans << endl;
}