#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 105;
int a[N],c[N];


int main() {
    int n;
    while(scanf("%d",&n)+1)
    {
        memset(c,0,sizeof(c));
        for(int i=1;i<=n;i++) scanf("%d",&a[i]),c[a[i]]++;
        int res=0;
        for(int i=1;i<100;i++) res=max(res,c[i]+c[i-1]);
        printf("%d\n",res);
    }
    return 0;
}