#include <cstdio>
#include <cstring>
#include <cmath>
#include <queue>
#include <cstring>
#include <vector>
#include <string>
#include <stack>
#include <set>
#include <map>
#include <iostream>
#include <algorithm>
using namespace std;
#define MP make_pair
#define PB push_back
typedef long long LL;
typedef pair<int, int> Pii;
const int inf = 0x3f3f3f3f;
const LL INF = (1uLL << 63) - 1;
const LL mod = 1000000007;
const double Pi = acos(-1.0);
const int maxn = 2e5 + 5;
#define mid (( l + r ) >> 1)
#define lson l,mid, o<<1
#define rson mid+1,r,o<<1|1
int n;
int cnt[105];
int main() {
#ifdef local
    freopen("in", "r", stdin);
#endif
    cin>>n;
    for(int i = 0 ; i < n ; i ++){
        int x;
        cin>>x;
        cnt[x]++;
    }
    int ret = 0 ;
    for(int i = 0 ; i <= 100; i++){
        ret = max(cnt[i]+cnt[i+1],ret);
    }
    cout<<ret<<endl;
}