#include <bits/stdc++.h>
using namespace std;
int n, nn, sum;
vector<double> q;
double x, ans, anss;
int main() {
  scanf("%d", &n);
  sum = 0;
  for (int i = 1; i <= 2 * n; i++) {
    scanf("%lf", &x);
    ans += (x - floor(x));
    if (floor(x) == ceil(x)) sum++;
  }
  if (sum > n) n = n * 2 - sum;
  sum = min(sum, n);
  anss = 10000000;
  for (int i = n - sum; i <= n; i++) anss = min(anss, fabs(ans - i));
  printf("%.3lf", anss);
}
