#include <bits/stdc++.h>
using namespace std;
int n;
double a[4010];
int main() {
  cin >> n;
  n *= 2;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int i = 1; i <= n; ++i) a[i] = a[i] - int(a[i]);
  int cnt = 0;
  for (int i = 1; i <= n; ++i)
    if (abs(a[i] - 0) <= 0.0000001) cnt++;
  double sum = 0;
  for (int i = 1; i <= n; ++i) sum += a[i];
  double res = 1000000001;
  for (int i = 0; i <= cnt; ++i) res = min(res, abs(n / 2 - sum - i));
  printf("%.3f", res);
}
