#include <bits/stdc++.h>

using namespace std;

int main(){
    int n;
    cin >> n;
    int arr[n];
    for(int i=0;i<n;i++)
        cin>>arr[i];
    int freq[100];
    for(int i=0;i<100;i++)
        freq[i]=0;
    sort(arr,arr+n);
    int ns = 1;
    int j;
    for(j=0;j<n-1;j++){
        if(arr[j+1]==arr[j])
            ns++;
        else{
            freq[arr[j]] = ns;
            ns = 1;
        }
    }
    freq[arr[n-1]]=ns;
    	
    int ans,max = 0;
    for(int k=0;k<99;k++){
        max = freq[k] + freq[k+1];
        if(max>ans)
            ans = max;
    }
    
    cout<<ans;
    
    return 0;
}