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


int main() {
    int n;
    scanf("%d",&n);
    int a[101]={0};
    for(int i=0;i<n;i++){
        int p;
        scanf("%d",&p);
        a[p]++;
    }
    int m=0;
    for(int i=0;i<100;i++){
        m=max(m,a[i]+a[i+1]);
    }
    printf("%d",m);
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}