#include<bits/stdc++.h>
using namespace std;
 
long long dp[500005][2], n, a[500005], cnt = 1;
 
int main()
{
    cin >> n;
    for (long long i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
 
    dp[a[1]][0] = 1;
 
    for (long long i = 2; i <= n; i++)
    {
 
        dp[a[i]][1] = max({dp[a[i]][1], dp[a[i] - 1][1] + 1,dp[a[i] - 2][0] + 2});
        dp[a[i]][0] = max({dp[a[i]][0], dp[a[i] - 1][0] + 1,1LL});
 
        cnt = max({cnt, dp[a[i]][0], dp[a[i]][1]});
    }
 
    cout << cnt;
}

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