1 #include <iostream> 2 using namespace std; 3 int main() 4 {int day,n,x1,x2; 5 cin>>n; 6 day=n-1; 7 x2=1; 8 while(day>0) 9 {x1=(x2+1)*2; 10 x2=x1; 11 day--; 12 } 13 cout<<x1<<endl; 14 return 0; 15 }
原文：http://www.cnblogs.com/wangmengmeng/p/4542567.html