1 /* 2     数学：假设取了第i个，有C(n-1)(i-1)种取法 3         则ans = sum (C(n-1)(i-1)) (1<=n) 即2^(n-1) 4 */ 5 #include 
      
        6 #include 
       
         7 #include 
        
          8 #include 
         
           9 using namespace std;10 11 typedef long long ll;12 const int MAXN = 1e4 + 10;13 const int INF = 0x3f3f3f3f;14 const int MOD = 1000000007;15 16 int main(void)        //FZU 2074 Number of methods17     int n;18     while (scanf ("%d", &n) == 1)19     {20         ll sum = 1;21         for (int i=1; i