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

#define mp make_pair
#define pb push_back
typedef long long ll;
typedef complex<double> point;
typedef pair<int, int> pii;
typedef vector<int> vi;

#define DEBUG 0
#define dout if(DEBUG) cout

const int MAXN = 100 + 5;
map<int, int> cnt;
int a[MAXN];

void solve(){
    int n;
    cin >> n;
    for(int i = 0; i < n; i++){
        cin >> a[i];
        cnt[a[i]]++;
    }
    int mx = 0;
    for(int i = 0; i < n; i++){
        mx = max(mx, cnt[a[i]] + (cnt.find(a[i] + 1) != cnt.end() ? cnt[a[i] + 1] : 0));
    }
    cout << mx;
}

int main() {
    #ifdef NASTYA
        assert(freopen("input.txt", "r", stdin)); assert(freopen("output.txt", "w", stdout));
    #else
     //assert(freopen(file".in", "r", stdin)); assert(freopen(file".out", "w", stdout));
    #endif
    int t = 1;
    while(t--) {
        solve();
    }
    return 0;
}