#include <iostream>
#include <vector>
 
using namespace std;
 
int countSpecialElements(vector<int>& nums) {
    int n = nums.size();
    vector<int> dp(n + 1, 0);
 
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < i; ++j) {
            if (nums[i] == nums[j] * 3) {
                dp[i + 1] = max(dp[i + 1], dp[j + 1] + 1);
            }
        }
        dp[i + 1] = max(dp[i + 1], dp[i]);
    }
 
    return dp[n];
}
 
int main() {
    int N;
    cin >> N;
 
    vector<int> nums(N);
    for (int i = 0; i < N; ++i) {
        cin >> nums[i];
    }
 
    cout << countSpecialElements(nums) << endl;
 
    return 0;
}
 

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