#include <iostream> using namespace std; void han(int n,char a,char b,char c){ if(n==1){ printf("%c %c\n",a,c); return; } han(n-1,a,c,b); printf("%c %c\n",a,c); han(n-1,b,a,c); } int main() { int n; scanf("%d",&n); han(n,'A','B','C'); return 0; }