#include <bits/stdc++.h>
using namespace std;
const int Maxn = 4010;
double num1[Maxn];
int num2[Maxn];
double dif[Maxn];
int main() {
  int n = 0, N = 0;
  int cnt = 0, cnt1 = 0, cnt2 = 0;
  double sum = 0;
  double ans = 100000000.0;
  scanf("%d", &n);
  N = 2 * n;
  for (int i = 0; i < N; i++) {
    scanf("%lf", &num1[i]);
    num2[i] = num1[i];
    dif[i] = (double)num1[i] - (double)num2[i];
  }
  for (int i = 0; i < N; i++) {
    if (dif[i] != 0) {
      cnt1++;
      sum += dif[i];
    } else {
      cnt2++;
    }
  }
  cnt = min(cnt1, n);
  for (int i = 0; i <= cnt; i++) {
    if (i + cnt2 >= n) {
      ans = min(ans, fabs(sum - i * 1.0));
    }
  }
  printf("%.3f", ans);
  return 0;
}
