猴子摘桃

#include <iostream>

using namespace std;
int f(int n){
    int num;
   if(n == 4){
    return 1;
   }
   else{
    num = (f(n+1)+1)*2;
   }
   return num;
}
int main()
{
   int num = f(1);
   cout<<num;
    return 0;
}