AC answer

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

int n;
int north[25],east[25],west[25];

void work()
{
cin>>n;
north[1]=east[1]=west[1]=1;
for(int i=2;i<=n;i++)
{
north[i]=east[i-1]+west[i-1]+north[i-1];
east[i]=north[i-1]+east[i-1];
west[i]=north[i-1]+west[i-1];
}
cout<<north[n]+east[n]+west[n];
}

int main()
{
work();
return 0;
}