~cpp
#include <iostream>
using namespace std;
int num(int val, int start, int end);
int main()
{
cout << num(3, 1, 2) << endl;
return 0;
}
int num(int val, int start, int end)
{
if(val == 1)
{
cout << start << "->" << end << endl;
return 1;
}
else
{
return num(val - 1, start, 6-start-end) + num(1,start,end) + num(val - 1, 6-start-end, end);
}
}