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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    int a[n],cnt[100]={0},max = 0;
    for(int i=0;i<n;i++) {cin>>a[i];cnt[a[i]]++;}
    for(int i=0;i<99;i++) if(cnt[i]!=0){
        if(cnt[i]+cnt[i+1]>max) max = cnt[i]+cnt[i+1];
    }
    cout<<max;
    return 0;
}