#include <bits/stdc++.h>

using namespace std;

int a[1000];

int main()
{
    //freopen("A.in","r",stdin);

    int N;
    cin >> N;

    for(int i = 1; i <= N; ++i){
        int x;
        cin >> x;
        a[x] ++;
    }
    int maxi = 0;
    for(int i = 0; i <= 200; ++i)
        maxi = max(maxi, a[i] + a[i+1]);
    
    cout << maxi;
    
    return 0;
}