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

typedef unsigned short usint;
typedef unsigned uint;
typedef long lint;
typedef short sint;
typedef unsigned long ulint;
typedef unsigned long long ullint;
typedef long long llint;

#define INF 1000000
#define mp make_pair
#define pii pair <int,int>
#define pll pair <long,long>
#define pui pair <uint,uint>
#define pul pair <ulint,ulint>
#define pull pair <ullint,ulint>
// inline funkcije


int main()
{
    ios_base::sync_with_stdio(0);


    int n;
    cin >> n;

    int A[n];
    int X[101];
    memset(X, 0, sizeof X);

    for (int t1 = 0; t1 < n; ++t1)
    {
        cin >> A[t1];
        X[A[t1]]++;
    }

    int maxc = 0, c = 0;

    for (int t1 = 1; t1 < n; ++t1)
    {
        maxc = max(maxc, X[t1]+X[t1-1]);
    }

    cout << maxc << '\n';
















    return 0;
}