#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    
    int b[100010],c[100010],m = -1;
    memset(c, 0, sizeof(c));
    for(int i=1; i<=n; i++)
    {
        scanf("%d",&b[i]); c[b[i]] ++;
        m = max(m, b[i]);
    }
    int ans = 0;
    for(int i=0; i<=m; i++)
        ans = max(ans, c[i]+c[i+1]+c[i+2]);
    cout << ans << endl;
    
    return 0;
}
