/* Don't overcomplicate. */
/* Don't construct unnecessary objects. */
/* Stack is for everything. */

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

#define MAX(T) (std::numeric_limits<T>::max())
using i8  = int_fast8_t;
using i16 = int_fast16_t;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
using u8  = uint_fast8_t;
using u16 = uint_fast16_t;
using u32 = uint_fast32_t;
using u64 = uint_fast64_t;
using st = size_t;
const std::string nl = "\n";

#define pb push_back
#define eb emplace_back
#define forn(n) fornn(_Temp_I_ ## __LINE__ ## __COUNTER__ ## _ ## __FILE__, (n))
#define fornn(name, n) for (size_t name{}; name < n; ++name)
#define what_is(x) (std::cerr << (#x) << " is " << (x) << std::endl)

int main()
{
    std::ios_base::sync_with_stdio(0);
    std::cin.tie(nullptr);  // disables automatic flush of std::cout before std::cin -- take care in interactive problems
    //std::ifstream   cin("TASKNAME.in");
    //std::ofstream  cout("TASKNAME.out");
    //std::cin.rdbuf(cin.rdbuf());
    //std::cout.rdbuf(cout.rdbuf());
    /*************** GOOD LUCK ***************/
    
    st n;
    cin >> n;
    vector<st> cnt(100);
    st x;
    
    for (st i = 0 ;i < n; i++)
    {
        cin >> x;
        cnt[x-1]++;
    }
    
    st m = 0;
    for (st i = 0; i < 99; i++)
    {
        if (m < cnt[i] + cnt[i+1])
            m = cnt[i] + cnt[i+1];
    }
    cout << m << nl;
        
        
}