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

// Time Complexity: O(n log n)
// Memory Complexity: O(n)

using ll = long long;

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);

	int n; cin >> n;
	vector<int> a(n);
	for(auto &x : a) cin >> x;
	map<int, int> dp;
	
	int ans = 0;
	for(int i = 0; i < n; i++) {
		dp[a[i]] = max(dp[a[i]], dp[a[i]-1]+1);
		ans = max(ans, dp[a[i]]);
	}

	cout << ans << "\n";

	return 0;
}