世界第一

#include <iostream>
using namespace std;

void dfs(int h, char start, char end, char middle) {
if (h == 0) {
return;
}
dfs(h - 1, start, middle, end);
cout << start << " --" << h << "--> " << end << "\n";
dfs(h - 1, middle, end, start);
}
int main() {
int n;
cin >> n;
dfs(n, 'A', 'C', 'B');
return 0;
}