The input will be twelve lines. Each line will contain the closing balance of his bank account for a particular month. Each number will be positive and displayed to the penny. No dollar sign will be included. 

The output will be a single number, the average (mean) of the closing balances for the twelve months. It will be rounded to the nearest penny, preceded immediately by a dollar sign, and followed by the end-of-line. There will be no other spaces or characters in the output. 

100.00
489.12
12454.12
1234.10
823.05
109.20
5.27
1542.25
839.18
83.99
1295.01
1.75

1581.42

题意：
　　将1~12月的money相加再除以12，得到的结果保留两位小数

C/C++代码实现（AC）;

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <cstring>
 4 #include <cstdio>
 5 #include <cmath>
 6 #include <stack>
 7 #include <map>
 8 #include <queue>
 9 #include <set>
10 
11 using namespace std;
12 const int MAXN = 310;
13 int A[MAXN];
14 
15 int main()
16 {
17     double a, cnt = 0.0;
18     for(int i = 0; i < 12; ++ i)
19     {
20         scanf("%lf", &a);
21         cnt += a;
22     }
23     printf("%.2lf", cnt / 12.0);
24     return 0;
25 }