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

int n, ans, x;
int a[105];

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    ~scanf("%d",&n);
    for(int i = 0; i < n; i++){
        ~scanf("%d",&x);
        a[x]++;
    }
    for(int i = 0; i <= 99; i++){
        ans = max(ans, a[i] + a[i + 1]);
    }
    printf("%d",ans);
    return 0;
}