poj 2646 The Trip

#include <iostream>
#include <algorithm>
#include <cstdio>
#define N 1100
using namespace std;
int main()
{
int i,n;
double a
;
while(cin>>n,n)
{
double sum=0,num1=0,num2=0;
for(i=0; i<n; i++) {
cin>>a[i];
sum+=a[i];
}
sum/=n;
int ave=sum*100+0.5;/*这个题的精粹，对于精度的取舍问题*/
sum=ave/100.0;
for(i=0; i<n; i++) {
if(a[i]<sum)
num1+=sum-a[i];
else
num2+=a[i]-sum;
}
if(num2<num1)
num1=num2;
printf("$%.2lf\n",num1);
}
return 0;
}