POJ上已经定义了ONLINE_JUDGE. 所以要用"ifndef", 本地IDE中的宏定义删了. scanf: %f小数点后6位 %G和%g 小数点后2位,但是自动会去除末尾的0

 
#include "stdio.h"

int main(void) {
    float c;
    float result=0.0;
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    #else
    #endif
    while((scanf("%G",&c))!=EOF){
          //printf("%Gn",c);
         result = result + c;
         //printf("%Gn",result);
    }

    printf("$%G",result/12);
    #ifndef ONLINE_JUDGE
    fclose(stdin);
    #else
    #endif
    return 0;
}