#include <stdio.h> int f(int n,char kaishi,char mid,char end) { int count=0; if(n==1) { count+=2; return count; } int sum=0; sum+=f(n-1,kaishi,mid,end); sum++; sum+=f(n-1,end,mid,kaishi); sum++; sum+=f(n-1,kaishi,mid,end); return sum; } int main() { int n; while(scanf("%d",&n)!=E...