View Code of Problem 3834

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstring>
#include <iostream>
#include <set>
#include <string>
#include <vector>
using namespace std;

int main()
{
    int n;
    long long arr[100] = {0};
    while (cin >> n)
    {
        arr[1] = 2;
        arr[2] = 5;
        for (int i = 3;i <= 90;i++){
            arr[i] = arr[i - 1] * 3 - 1;
        }
        cout << arr[n] << endl;
    }
}