#include <bits/stdc++.h>
using namespace std;
int N;
int main() {
  cin >> N;
  int dec[2 * N];
  int all_round_down = 0;
  int z = 0;
  for (int i = 0; i < 2 * N; i++) {
    double x;
    cin >> x;
    dec[i] = int((x + 0.0005 - int(x + 0.0005)) * 1000);
    all_round_down += dec[i];
    if (dec[i] == 0) z++;
  }
  int mi = max(0, N - z);
  int ma = min(N, 2 * N - z);
  int best = (all_round_down + 500) / 1000;
  int ans;
  if (best >= mi && best <= ma)
    ans = abs(all_round_down - 1000 * best);
  else
    ans = min(abs(all_round_down - 1000 * mi), abs(all_round_down - 1000 * ma));
  cout << ans / 1000 << "." << (ans % 1000) / 100 << (ans % 100) / 10
       << ans % 10;
}
