#include<bits/stdc++.h>
using namespace std;
int arr[100010], brr[100010]={0}, len[100010] = {0};
int main()
{
   int num=1, m=0, n,c;
   cin >> n;
   for (int i = 0; i < n; i++)
   {
   	cin >> arr[i];
   }
   sort(arr, arr + n);
   for (int i = 0; i < n; i++)
   {
   	bool find = 0;
   	for (int j = 0; j < m; j++)
   	{
   		if (arr[i]==brr[j]+1)
   		{
   			brr[j] = arr[i];
   			len[j]++;
   			find = 1;
   			j = m;
   		}
   	}
   	if (!find)
   	{
   		brr[m] = arr[i];
   		len[m]++;
   		m++;
   	}
   }
   sort(len, len + m);
   cout <<len[0];
}