#include<iostream>
#include<string>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<cstdio>
#include<iomanip>
#include<stack>
#include<queue>
#include<deque>
using namespace std;
int main(){
    //freopen("test.in","r",stdin);
    //freopen("test.out","w",stdout);
	double money,a;
	for(int i=0;i<12;i++){
		cin>>money;
		a+=money;
	}
	double x=a/12;
	printf("$%.2f",x);
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}

题目