/******************************************
*    AUTHOR:         BHUVNESH JAIN        *
*    INSTITUITION:   BITS PILANI, PILANI  *
******************************************/
#include <bits/stdc++.h>
using namespace std;
 
typedef long long LL; 
typedef long double LD;

int f[101];

int main() {
	#ifndef ONLINE_JUDGE
		// freopen("inp.txt", "r", stdin);
	#endif
	int n, a;
	scanf("%d", &n);
	for(int i = 1; i <= n; ++i) {
		scanf("%d", &a);
		f[a] += 1;
	}
	int ans = f[1];
	for(int i = 2; i < 101; ++i) {
		ans = max(ans, f[i] + f[i-1]);
	}
	printf("%d\n", ans);
	return 0;
}