#include<bits/stdc++.h>
#define ll long long int
using namespace std;
 
int longestConsecutive(const vector<int> &A) {
    unordered_map<int,int> mp;
    int l1,l2;
    for(int i=0;i<A.size();i++) {
        if(mp.find(A[i]-1)!=mp.end() || mp.find(A[i]+1)!=mp.end()) {
            l1=mp[A[i]-1];
            if(mp.find(A[i]+1)!=mp.end())
            l2=mp[A[i]+1];
            int l=l1+l2+1;
            int LB=A[i]-l1;
            int RB=A[i]+l2;
            mp[LB]=l;
            if(mp.find(A[i]+1)!=mp.end())
            mp[RB]=l;
            mp.insert({A[i],l});
        }
        else mp[A[i]]=1;
    }
    int res=mp[A[0]];
    for(int i=1;i<A.size();i++) {
        res=max(res,mp[A[i]]);
    }
    return res;
}
 
 
int main() {
	int n;
	cin>>n;
	vector<int> a(n);
	for(int i=0;i<n;i++)
	    cin>>a[i];
	 cout<<"\n"<<longestConsecutive(a);
}