#include<bits/stdc++.h>
#define ll long long int
#define mp make_pair
#define pb push_back
#define si(x) scanf("%d",&x)
#define pi(x) printf("%d\n",x)
#define s(x) scanf("%lld",&x)
#define p(x) printf("%lld\n",x)
#define sc(x) scanf("%s",x)
#define pc(x) printf("%s",x)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pis pair<string,int>
#define F first
#define S second
#define M 1000000007
#define N 102
#define inf 1e9+10

using namespace std;

int cnt[N];
int main(){
int n;
si(n);
for(int i=0;i<n;i++){
    int x; si(x);
    cnt[x]++;
}
int ans=0;
for(int i=1;i<99;i++){
    int temp=cnt[i]+cnt[i+1];
    ans=max(ans,temp);
}
pi(ans);

return 0;
}