#include<bits/stdc++.h>
using namespace std;
 
#define MP make_pair
#define pb push_back
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define PER(i,a,b) for(int i=b;i>=a;i--)
#define X first
#define Y second
 
//i/o
#define inp(n) scanf("%d",&n)
#define inpl(n) scanf("%lld",&n)
#define inp2(n,m) inp(n), inp(m)
#define inp2l(n,m) inpl(n), inpl(m)
 
 
//cost
#define lli long long int
#define MOD 1000000007
#define MOD_INV 1000000006
#define MAX 100009
#define INF 999999999
#define mp make_pair
 
//iterators
#define vitr std::vector<int>::iterator

int main()
{
    int n, A[105], hash[105]={0}, max = -1;
    inp(n);

    rep(i,n)
    {
        inp(A[i]);
        hash[A[i]]++;
    }

    for (int i = 1; i <= 100; ++i)
    {
        if(max < (hash[i] + hash[i+1]))
        {
            max = hash[i] + hash[i+1];
        }
    }

    printf("%d\n", max);
    return 0;
}