#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define F first
#define S second
#define sd(x) scanf("%d", &x)
#define sl(x) scanf("%lld", &x)
#define ss(x) scanf("%s", x)
#define sc(x) scanf(" %c", &x)
#define sz(x) x.size()
#define debug(X) cerr << " --> " << #X << " = " << X << endl
#define clr(x) memset(x, 0, sizeof x)
#define all(x) x.begin(), x.end()
#define rep(i, begin, end) for(__typeof(end) i =(begin)-((begin)>(end));i!=(end)-((begin)>(end));i+=1-2*((begin)>(end)))
#define endl "\n"
typedef long long ll; typedef pair<int, int> pii; typedef vector<int> vi;
const int N = 112345, LG = 21, mod = 1000000007, M = N;
const double eps = 1e-3, pi = acos(-1.0);
const ll INF = 1123456789123456789LL;
bool sieve[N];
int pre[N], ct[N];
int main()
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    int n, x;
    sd(n);
    rep(i, 0, n)
        sd(x), ct[x] += 1;
    int ans = 0;
    rep(i, 0, 101)
        ans = max(ans, ct[i] + ct[i + 1]);
    printf("%d\n", ans);
    return 0;
}