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

typedef unsigned long long ull;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef  vector<unsigned long long > vull;

#define pb push_back
#define mp make_pair
#define X first
#define Y second

#define rep(i,n) for(int i=0;i<(n);i++)
#define Rep(i,a,b) for(int i=(a);i<(b);i++)
#define repr(i,n) for(int i=(n-1);i>=0;i--)
#define wh(t) while(t--)
#define all(x) (x).begin(),(x).end()
#define sz(a) a.size()

#define MOD 1000000007
#define PI 3.14159265358979
#define endl '\n'

inline int sd()
{
	register char c=getchar_unlocked();
	int n=0;
	while(c<'0'||c>'9') c=getchar_unlocked();
	for(;c>='0'&&c<='9';c=getchar_unlocked())
	n=(n<<1)+(n<<3)+(c-'0');
	return n;
}

inline void pd(ull n)
{
	char c[20];
	int i=0;
	do
	{
	c[i++]=n%10+'0';
	n/=10;
	}while(n!=0);
	i--;
	while(i>=0)
	putchar_unlocked(c[i--]);
	putchar_unlocked('\n');
}


int main()
{
	//ios_base::sync_with_stdio(false);
	//cin.tie(NULL);
	int c[101]={0};
	int n,x,m=0;
	n=sd();
	rep(i,n)
	{
		x=sd();
		c[x]++;
	}
	rep(i,100)
	{

		m=max(m,c[i]+c[i+1]);
	}
	pd(m);
	return 0;
}